Programming and Data Types in C programming

In C programming we have different kinds of data types in C language and this is in continuation with previous discussion.

Integers signed and unsigned:

Sample code for syntax for unsigned inter is :

nsigned int num_students ;

With this declaration, the range of permissible integer values (for a 16-bit OS) will shift from the range -32768 to +32767 to the range 0 to 65535. Thus, declaring an integer as unsigned almost doubles the size of the largest possible value that it can otherwise take.

It happens because on declaring the integer as unsigned, the left-most bit is now free and is not used to store the sign of the number.

Unsigned integer still occupies two bytes.

It can be declared as : unsigned int i ; unsigned i ;

There also exists a short unsigned int and a long unsigned int. By default a short int is a signed short int and a long int is a signed long int in C programming.

Chars, signed and unsigned

Signed and unsigned chars, both occupying one byte each, but having different ranges. Consider the statement

char ch = 'A' ;

Here what gets stored in ch is the binary equivalent of the ASCII value of ‘A’ (i.e. binary of 65). And if 65’s binary can be stored, then -54’s binary can also be stored (in a signed char).

A signed char is same as an ordinary char and has a range from -128 to +127; whereas, an unsigned char has a range from 0 to 255.

Floats and Doubles

A float occupies four bytes in memory and can range from -3.4e38 to +3.4e38. If this is insufficient then C offers a double data type that occupies 8 bytes in memory and has a range from -1.7e308 to +1.7e308.

A variable of type double can be declared as,

double a, population ;

If the situation demands usage of real numbers that lie even beyond the range offered by double data type, then there exists a long double that can range from -1.7e4932 to +1.7e4932.

A long double occupies 10 bytes in memory in c programming and it is used rarely.

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C PROGRAM INSTRUCTIONS

COMPILATION AND EXECUTION OF C PROGRAM

Programming and Data Types

Primary data types of programming could be of three varieties—char, int, and float. We can derive many data types from these three types.

A char could be an unsigned char or a signed char. Or an int could be a short int or a long int.

Integers, long and short We had seen earlier that the range of an Integer constant depends upon the compiler.

For a 16-bit compiler like Turbo C or Turbo C++ the range is –32768 to 32767.
For a 32-bit compiler the range would be –2147483648 to +2147483647.

16-bit compiler means that when it compiles a C program it generates machine language code that is targeted towards working on a 16-bit microprocessor like Intel 8086/8088.

A 32-bit compiler like VC++ generates machine language code that is targeted towards a 32-bit microprocessor like Intel Pentium.
A program compiled using Turbo C would not work on 32-bit processor. It would run successfully but at that time the 32-bit processor would work as if it were a 16-bit processor.

This happens because a 32-bit processor provides support for programs compiled using 16-bit compilers. If this backward compatibility support is not provided the 16-bit program would not run on it.

Out of the two or four bytes used to store an integer, the highest bit (16th/32nd bit) is used to store the sign of the integer. This bit is 1 if the number is negative, and 0 if the number is positive.

C offers a variation of the integer data type that provides what are called short and long integer values.

Short and long integers would usually occupy two and four bytes respectively. Each compiler can decide appropriate sizes depending on the operating system and hardware for which it is being written, subject to the following rules:

• shorts are at least 2 bytes big
• longs are at least 4 bytes big
• shorts are never bigger than ints
• ints are never bigger than longs

long variables which hold long integers are declared using the keyword long.

Long integers cause the program to run a bit slower, but the range of values that we can use is expanded tremendously. The value of a long integer typically can vary from -2147483648 to +2147483647.

Integers that need less space in memory and thus help speed up program execution.

Short integer variables are declared as,

short int j ;
short int height ;

C allows the abbreviation of short int to short and of long int to long. So the declarations made above can be written as,

long i ;
long abc ;
short j ;
short height ;

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INTRODUCTION TO C PROGRAMMING

Programming with C an introduction part two

Data types for C programming

C PROGRAMMING CHARACTER SET

CONSTANTS IN C PROGRAMMING

PROGRAMMING C VARIABLES

C PROGRAM INSTRUCTIONS

COMPILATION AND EXECUTION OF C PROGRAM

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C PROGRAMMING RULES PART TWO

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FUNCTIONS IN C PROGRAMMING

Functions and usage in C part two

Coding in C functions

Programming C Functions Coding

Programming with C language and using Functions is done in our previous discussions. Now we are going to deal with advanced concepts of using functions in c programming.

Function Declaration and Prototypes :

Any C function by default returns an int value. Whenever a call is made to a function, the compiler assumes that this function would return a value of the type int. If a function should return a value other than an int, then it is necessary to explicitly mention so in the calling function as well as in the called function.

The following program segment illustrates how to make square( ) capable of returning a float value.

main( )
{
float square ( float ) ;
float a, b ;
printf ( "\nEnter any number " ) ;
scanf ( "%f", &a ) ;
b = square ( a ) ;
printf ( "\nSquare of %f is %f", a, b ) ;
}
float square ( float x )
{
float y ;
y = x * x ;
return ( y ) ;
}

And here is the output

Enter any number 1.5 Square of 1.5 is 2.250000
Enter any number 2.5 Square of 2.5 is 6.250000

The function square( ) must be declared in main( ) as float square ( float ) ;

This statement is often called the prototype declaration of the square( ) function. What it means is square( ) is a function that receives a float and returns a float.

Call by Value and Call by Reference

Whenever a function is called and passed something to it we have always passed the ‘values’ of variables to the called function. Such function calls are called ‘calls by value’. On calling a function we are passing values of variables to it.

Call by reference is done with pointers in C programming.

Pointer Notation Consider the declaration, int i = 3 ;

This declaration tells the C compiler to

1. Reserve space in memory to hold the integer value.
2.Associate the name i with this memory location.
3. Store the value 3 at this location.

The computer has selected memory location 65524 as the place to store the value 3. The location number 65524 is not a number to be relied upon, because some other time the computer may choose a different location for storing the value 3. The important point is, i’s address in memory is a number.

TO print this address number

main( )
{
int i = 3 ;
printf ( "\nAddress of i = %u", &i ) ;
printf ( "\nValue of i = %d", i ) ;
}

The output of the above program would be: Address of i = 65524 Value of i = 3

‘&’ used in this statement is C’s ‘address of’ operator. The expression &i returns the address of the variable i, which in this case happens to be 65524. Since 65524 represents an address, there is no question of a sign being associated with it.

Hence it is printed out using %u, which is a format specifier for printing an unsigned integer.

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Programming with C and C Sharp
INTRODUCTION TO C PROGRAMMING

Programming with C an introduction part two

Data types for C programming

C PROGRAMMING CHARACTER SET

CONSTANTS IN C PROGRAMMING

PROGRAMMING C VARIABLES

C PROGRAM INSTRUCTIONS

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C PROGRAMMING RULES PART TWO

COMPILATION AND EXECUTION OF C PROGRAM

INSTRUCTIONS TO WRITE C PROGRAM

ARITHMETIC INSTRUCTIONS TO WRITE C PROGRAM

CONVERSION OF CONSTANTS IN C PROGRAM

PRIORITY OF AR THEMATIC OPERATIONS IN C

OPERATORS ASSOCIATIVITY IN C

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Functions and usage in C part two

Coding in C functions

Programming Functions in C part two

Previously we had discussed regarding the usage functions in C programming and this is a continuation for it.

Use of Functions in C programming

Writing functions avoids rewriting the same code over and over.

Explanation : Suppose we have a section of code in your program that calculates area of a triangle. If later in the program we want to calculate the area of a different triangle, we nee d not write the entire code once again and we would prefer to jump to a ‘section of code’ that calculates area and then jump back to the place from where you left off. This section of code is nothing but a function.

Using functions it becomes easier to write programs and keep track of what they are doing. If the operation of a program can be divided into separate activities, and each activity placed in a different function, then each could be written and checked more or less independently. Separating the code into modular functions also makes the program easier to design and understand.

We have to break a program into small units and write functions for each of isolated sub divisions. We can even write functions that are called only once and these functions perform some logically isolated task.

How to Pass Values between Functions ?

The mechanism used to convey information to the function is the ‘argument’. We use the arguments in the printf( ) and scanf( ) functions; the format string and the list of variables used inside the parentheses in these functions are arguments. The arguments are sometimes also called ‘parameters’.

Sending and receiving values between functions Example

Consider the following program where, in main( ) we receive the values of a, b and c through the keyboard and then output the sum of a, b and c.

The calculation of sum is done in a different function called calsum( ). If sum is to be calculated in calsum( ) and values of a, b and c are received in main( ), then we must pass on these values to calsum( ), and once calsum( ) calculates the sum we must return it from calsum( ) back to main( ).

main( )

{

int a, b, c, sum ;

printf ( "\nEnter any three numbers " ) ;

scanf ( "%d %d %d", &a, &b, &c ) ;

sum = calsum ( a, b, c ) ;

printf ( "\nSum = %d", sum ) ;

}

calsum ( x, y, z )

int x, y, z ;

{

int d ;

d = x + y + z ;

return ( d ) ;

}


And here is the output... Enter any three numbers 10 20 30 Sum = 60

Explanation

1.In this program, from the function main( ) the values of a, b and c are passed on to the function calsum( ), by making a call to the function calsum( ) and mentioning a, b and c in the parentheses: sum = calsum ( a, b, c ) ; In the calsum( ) function these values get collected in three variables x, y and z:

calsum ( x, y, z )

int x, y, z ;

2.The variables a, b and c are called ‘actual arguments’, whereas the variables x, y and z are called ‘formal arguments’. Any number of arguments can be passed to a function being called. The type, order and number of the actual and formal arguments must always be same.

3.The return statement serves two purposes:
1. On executing the return statement it immediately transfers the control back to the calling program.
2. It returns the value present in the parentheses after return, to th3e calling program.

4.There is no restriction on the number of return statements that may be present in a function. Also, the return statement need not always be present at the end of the called function.

5.Whenever the control returns from a function some value is definitely returned. If a meaningful value is returned then it should be accepted in the calling program by equating the called function to some variable.

6.If we want that a called function should not return any value, we must mention so by using the keyword void .

void display( )
{
printf ( "\nHeads I win..." ) ;
printf ( "\nTails you lose" ) ;

7.A function can return only one value at a time.

OTHER PROGRAMMING COURSES:
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Programming with C an introduction part two

Data types for C programming

C PROGRAMMING CHARACTER SET

CONSTANTS IN C PROGRAMMING

PROGRAMMING C VARIABLES

C PROGRAM INSTRUCTIONS

COMPILATION AND EXECUTION OF C PROGRAM

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C PROGRAMMING RULES PART TWO

COMPILATION AND EXECUTION OF C PROGRAM

INSTRUCTIONS TO WRITE C PROGRAM

ARITHMETIC INSTRUCTIONS TO WRITE C PROGRAM

CONVERSION OF CONSTANTS IN C PROGRAM

PRIORITY OF AR THEMATIC OPERATIONS IN C

OPERATORS ASSOCIATIVITY IN C

IF STATEMENT

MULTIPLE STATEMENTS IN IF

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NESTED IF AND ELSE

BREAK

CONTINUE AND DO WHILE IN C LANGUAGE

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FUNCTIONS IN C PROGRAMMING

Functions and usage in C part two

Coding in C functions

Programming C Language Introduction

C programming language is said to be a middle level language because it combines the best elements of high-level languages with the control and flexibility of assembly language .

As a middle-level language, C allows the manipulation of bits, bytes, and addresses the basic elements with which the computer functions and C code is also very portable.Portability means that it is easy to adapt software written for one type of computer or operating system to another type.

All high level programming languages support the concept of data types. A data type defines a set of values that a variable can store along with a set of operations that can be performed on that variable. Common data types are integer, character, and floating-point. Although C has several built in data types, it is not a strongly typed language, as are Pascal and Ada. C permits almost all type conversions.

C specifies almost no run time error checking. For example, no check is performed to ensure that array boundaries are not overrun. and these types of checks are the responsibility of the programmer.

C does not demand strict type compatibility between a parameter and an argument.C allows an argument to be of any type so long as it can be reasonably converted into the type of the parameter and C provides all of the automatic conversions to accomplish this.

C allows the direct manipulation of bits, bytes, words, and pointers. This makes it well suited for system-level programming, where these operations are common.

C has only a small number of keywords, which are the commands that make up the C language. For example, C89 defined 32 keywords, and C99 adds only 5 more. High-level languages typically have many more keywords.

C is a structured language. The distinguishing feature of a structured language is compartmentalization of code and data. This is the ability of a language to section off and hide from the rest of the program all information and instructions necessary to perform a specific task. One way that you achieve compartmentalization is by using subroutines that employ local (temporary) variables.

By using local variables, you can write subroutines so that the events that occur within them cause no side effects in other parts of the program. This capability makes it very easy for your C programs to share sections of code. If you develop compartmentalized functions, you need to know only what a function does, not how it does it.

Structured languages typically support several loop constructs, such as while, do-while, and for. In a structured language, the use of goto is either prohibited or discouraged and is not the common form of program control . A structured language allows you to place statements anywhere on a line and does not require a strict field concept.

In C, functions are the building blocks in which all program activity occurs. They allow you to define and code individually the separate tasks in a program, thus allowing your programs to be modular.

After you have created a function, you can rely on it to work properly in various situations without creating side effects in other parts of the program. Being able to create stand alone functions is extremely important in larger projects where one programmer's code must not accidentally affect another's.

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Functions and usage in C part two

Coding in C functions

Function in C Programming

A computer program (except for the simplest one) cannot handle all the tasks by itself. Instead, it requests other program like entities—called ‘functions’ in C—to get its tasks done.

A function is a self-contained block of statements that perform a coherent task of some kind.

Example

main( )

{

message( ) ;

printf ( "\nCry!" ) ;

}

message( )

{ printf ( "\nSmile" ) ;

}

And here’s the output...

Smile...

Cry

Here, main( ) itself is a function and through it we are calling the function message( ). Main( ) ‘calls’ the function message( ) and it mean that the control passes to the function message( ).

The activity of main( ) is temporarily suspended; it falls asleep while the message( ) function wakes up and goes to work. When the message( ) function runs out of statements to execute, the control returns to main( ), which comes to life again and begins executing its code at the exact point where it left off. Thus, main( ) becomes the ‘calling’ function, whereas message( ) becomes the ‘called’ function.

Important points about Function

Any C program contains at least one function.

If a program contains only one function, it must be main( ).

If a C program contains more than one function, then one (and only one) of these functions must be main( ), because program execution always begins with main( ).

There is no limit on the number of functions that might be present in a C program.

Each function in a program is called in the sequence specified by the function calls in main( ).

After each function has done its thing, control returns to main( ).

When main( ) runs out of function calls, the program ends. The program execution always begins with main( ). Except for this all C functions enjoy a state of perfect equality. No precedence, no priorities.

One function can call another function it has already called but has in the meantime left temporarily in order to call a third function which will sometime later call the function that has called it.

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Switch statement in c programming
INTRODUCTION TO C PROGRAMMING

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C PROGRAMMING CHARACTER SET

CONSTANTS IN C PROGRAMMING

PROGRAMMING C VARIABLES

C PROGRAM INSTRUCTIONS

COMPILATION AND EXECUTION OF C PROGRAM

C PROGRAMMING RULES PART ONE

C PROGRAMMING RULES PART TWO

COMPILATION AND EXECUTION OF C PROGRAM

INSTRUCTIONS TO WRITE C PROGRAM

ARITHMETIC INSTRUCTIONS TO WRITE C PROGRAM

CONVERSION OF CONSTANTS IN C PROGRAM

PRIORITY OF AR THEMATIC OPERATIONS IN C

OPERATORS ASSOCIATIVITY IN C

IF STATEMENT

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BREAK

CONTINUE AND DO WHILE IN C LANGUAGE

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FUNCTIONS IN C PROGRAMMING

Functions and usage in C part two

Coding in C functions

Switch in C Programming

The control statement that allows us to make a decision from the number of choices is called a switch, or more correctly a switch-case-default, since these three keywords go together to make up the control statement.

The syntax for this is

switch ( integer expression )
{
case constant 1 :
do this ;
case constant 2 :
do this ;
case constant 3 :
do this ;
default : do this ;
}

The integer expression following the keyword switch is any C expression that will yield an integer value. It could be an integer constant like 1, 2 or 3, or an expression that evaluates to an integer. The keyword case is followed by an integer or a character constant. Each constant in each case must be different from all the others. The “do this” lines in the above form of switch represent any valid C statement.

How it functions ?

First, the integer expression following the keyword switch is evaluated. The value it gives is then matched, one by one, against the constant values that follow the case statements. When a match is found, the program executes the statements following that case, and all subsequent case and default statements as well. If no match is found with any of the case statements, only the statements following the default are executed.

Example with only Switch

main( )
{
int i = 2 ;
switch ( i )
{
case 1 :
printf ( "I am in case 1 \n" ) ;
case 2 : printf ( "I am in case 2 \n" ) ;
case 3 : printf ( "I am in case 3 \n" ) ;
default : printf ( "I am in default \n" ) ;
}
}

The output of this program would be:

I am in case 2
I am in case 3
I am in default

The switch executes the case where a match is found and all the subsequent cases and the default as well.

If you want that only case 2 should get executed, it is upto you to get out of the switch then and there by using a break statement.There is no need for a break statement after the default, since the control comes out of the switch anyway.

Example with Break statement and Switch

main( )
{
int i = 2 ;
switch ( i )
{
case 1 : printf ( "I am in case 1 \n" ) ;
break ;
case 2 : printf ( "I am in case 2 \n" ) ;
break ;
case 3 : printf ( "I am in case 3 \n" ) ;
break ;
default : printf ( "I am in default \n" ) ;
}
}

The output of this program would be:

I am in case 2

Other C programming Related topics are

INTRODUCTION TO C PROGRAMMING

Programming with C an introduction part two

Data types for C programming

C PROGRAMMING CHARACTER SET

CONSTANTS IN C PROGRAMMING

PROGRAMMING C VARIABLES

C PROGRAM INSTRUCTIONS

COMPILATION AND EXECUTION OF C PROGRAM

C PROGRAMMING RULES PART ONE

C PROGRAMMING RULES PART TWO

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INSTRUCTIONS TO WRITE C PROGRAM

ARITHMETIC INSTRUCTIONS TO WRITE C PROGRAM

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PRIORITY OF AR THEMATIC OPERATIONS IN C

OPERATORS ASSOCIATIVITY IN C

IF STATEMENT

MULTIPLE STATEMENTS IN IF

IF AND ELSE

NESTED IF AND ELSE

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Functions and usage in C part two

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Continue and do-while In C Language

When continue is encountered inside any loop, control automatically passes to the beginning of the loop. A continue is usually associated with an if.

Example :

main( )

{

int i, j ;

for ( i = 1 ; i <= 2 ; i++ ) { for ( j = 1 ; j <= 2 ; j++ ) { if ( i == j ) continue ; printf ( "\n%d %d\n", i, j ) ; } } } The output of the above program would be... 1 2 2 1 The continue statement takes the control to the for loop (inner) bypassing rest of the statements pending execution in the for loop (inner). The do-while Loop

The do-while loop looks like this:

do
{
this ;
and this ;
and this ;
and this ;
} while ( this condition is true ) ;

The difference between the working of while and do-while loops. This difference is the place where the condition is tested. The while tests the condition before executing any of the statements within the while loop. As against this, the do-while tests the condition after having executed the statements within the loop.

This means that do-while would execute its statements at least once, even if the condition fails for the first time. The while, on the other hand will not execute its statements if the condition fails for the first time.
The previous post of the blog deals with Requirements testing technique.

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UNIT TESTING PART ONE

UNIT TESTING PART TWO

UNIT TESTING PART THREE

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WINDOWS COMPLIANCE GUI TESTING PART ONE

WINDOWS COMPLIANCE GUI TESTING PART TWO

WINDOWS COMPLIANCE GUI TESTING PART THREE

WINDOWS COMPLIANCE GUI TESTING PART FOUR VALIDATION TESTING

WINDOWS COMPLIANCE GUI TESTING PART FIVE CONDITION TESTING

WINDOWS COMPLIANCE GUI TESTING PART SIX GENERAL CONDITION TESTING

Break Statement in C Programming

When break is encountered inside any loop, control automatically passes to the first statement after the loop. A break is usually associated with an if.

Example: Write a program to determine whether a number is prime or not. A prime number is one, which is divisible only by 1 or itself.

All we have to do to test whether a number is prime or not, is to divide it successively by all numbers from 2 to one less than itself. If remainder of any of these divisions is zero, the number is not a prime. If no division yields a zero then the number is a prime number.

Following program implements this logic.

main( )
{
int num, i ;
printf ( "Enter a number " ) ;
scanf ( "%d", &num ) ;
i = 2 ;
while ( i <= num - 1 ) { if ( num % i == 0 ) { printf ( "Not a prime number" ) ; break ; } i++ ; } if ( i == num ) printf ( "Prime number" ) ; } In this program the moment num % i turns out to be zero, (i.e. num is exactly divisible by i) the message “Not a prime number” is printed and the control breaks out of the while loop. There are two ways the control could have reached outside the while loop: 1 . It jumped out because the number proved to be not a prime. 2. The loop came to an end because the value of i became equal to num. When the loop terminates in the second case, it means that there was no number between 2 to num - 1 that could exactly divide num. That is, num is indeed a prime. If this is true, the program should print out the message “Prime number”. The keyword break, breaks the control only from the while in which it is placed. The following is the example to explain this point. main( ) { int i = 1 , j = 1 ; while ( i++ <= 100 ) { while ( j++ <= 200 ) { if ( j == 150 ) break ; else printf ( "%d %d\n", i, j ) ; } } } In this program when j equals 150, break takes the control outside the inner while only, since it is placed inside the inner while. The previous post of the blog deals with nested if statement of IF'S.

Learn complete course of C Programming here.

CONVERSION OF CONSTANTS IN C PROGRAM

PRIORITY OF AR THEMATIC OPERATIONS IN C

OPERATORS ASSOCIATIVITY IN C

IF STATEMENT

MULTIPLE STATEMENTS IN IF

IF AND ELSE

NESTED IF AND ELSE

BREAK

CONTINUE AND DO WHILE IN C LANGUAGE

SWITCH IN C PROGRAMMING

FUNCTIONS IN C PROGRAMMING

Functions and usage in C part two

Coding in C functions


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ASP.NET part one and two

Programming with C and C Sharp

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asp.net part one part two

Software Testing Complete course part one two and Interview Questions

Nested IF ELSES in C Programming

We can use to write an entire if-else construct within either the body of the if statement or the body of an else statement. This is called ‘nesting’of ifs.

Note that the second if-else construct is nested in the first else statement. If the condition in the first if statement is false, then the condition in the second if statement is checked. If it is false as well, then the final else statement is executed.

You can see in the program how each time a if-else construct is nested within another if-else construct, it is also indented to add clarity to the program. Inculcate this habit of indentation, otherwise you would end up writing programs which nobody (you included) can understand easily at a later date.

In the sample program an if-else occurs within the else block of the first if statement. Similarly, in some other program an if-else may occur in the if block as well. There is no limit on how deeply the ifs and the elses can be nested.

Here is the sample code to execute the nested if else statements.

main( )

{

int i ;

printf ( "Enter either 1 or 2 " ) ;

scanf ( "%d", &i ) ;

if ( i == 1 )

printf ( "You would go to heaven !" ) ;

else

{

if ( i == 2 )

printf ( "Hell was created with you in mind" ) ;

else

printf ( "How about mother earth !" ) ;

}

}

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IF - ELSE Statements

The if statement by itself will execute a single statement, or a group of statements, when the expression following if evaluates to true. It does nothing when the expression evaluates to false.To execute one group of statements if the expression evaluates to true and another group of statements if the expression evaluates to false we use the else statement .

Example:

In a company an employee is paid as under:

salary and DA = 90% of basic salary. If his salary is either equal to or above Rs. 1500, then HRA = Rs. 500 and DA = 98% of basic salary. If the employee's salary is input through the keyboard write a program to find his gross salary.

main( )

{

float bs, gs, da, hra ;

printf ( "Enter basic salary " ) ;

scanf ( "%f", &bs ) ;

if ( bs <>

{

hra = bs * 10 / 100 ;

da = bs * 90 / 100 ;

}

else

{

hra = 500 ;

da = bs * 98 / 100 ;

}

gs = bs + hra + da ;

printf ( "gross salary = Rs. %f", gs ) ;

}

The flow of control is given as shown below.

Here are the few points to concentrate further.

1 . The group of statements after the if up to and not including the else is called an ‘if block’. Similarly, the statements after the else form the ‘else block’.

2 . Notice that the else is written exactly below the if. The statements in the if block and those in the else block have been indented to the right. This formatting convention is followed throughout the book to enable you to understand the working of the program better.

3 . Had there been only one statement to be executed in the if block and only one statement in the else block we could have dropped the pair of braces.

4 . As with the if statement, the default scope of else is also the statement immediately after the else. To override this default scope a pair of braces as shown in the above example must be used.
78.2

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Mulitple Statements with in IF

It may so happen that in a program we want more than one statement to be executed if the expression following if is satisfied. If such multiple statements are to be executed then they must be placed within a pair of braces as illustrated in the following example.
Example : The current year and the year in which the employee joined the organization are entered through the keyboard. If the number of years for which the employee has served the organization is greater than 3 then a bonus of Rs. 2500/- is given to the employee. If the years of service are not greater than 3, then the program should do nothing.

Here is the sample code :
main( )
{
int bonus, cy, yoj, yr_of_ser ;
printf ( "Enter current year and year of joining " ) ;
scanf ( "%d %d", &cy, &yoj ) ;
yr_of_ser = cy - yoj ;
if ( yr_of_ser > 3 )
{
bonus = 2500 ;
printf ( "Bonus = Rs. %d", bonus ) ;
}
}

Observe that here the two statements to be executed on satisfaction of the condition have been enclosed within a pair of braces.

If a pair of braces is not used then the C compiler assumes that the programmer wants only the immediately next statement after the if to be executed on satisfaction of the condition. In other words we can say that the default scope of the if statement is the immediately next statement after it.

Here is the flow chart of the sequence of above program.

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If Statement in C Programming

C uses the keyword if to implement the decision control instruction. The general form of if statement looks like this:

if ( this condition is true )

execute this statement ;

The keyword if tells the compiler that what follows is a decision control instruction. The condition following the keyword if is always enclosed within a pair of parentheses. If the condition, whatever it is, is true, then the statement is executed. If the condition is not true then the statement is not executed; instead the program skips past it.

As a general rule, we express a condition using C’s ‘relational’ operators. The relational operators allow us to compare two values to see whether they are equal to each other, unequal, or whether one is greater than the other. Here’s how they look and how they are evaluated in C.

Sample program to execute C Program :

main( )
{
int num ;
printf ( "Enter a number less than 10 " ) ;
scanf ( "%d", &num ) ;
if ( num <= 10 ) printf ( "What an obedient servant you are !" ) ; } On execution of this program, if you type a number less than or equal to 10, you get a message on the screen through printf( ). If you type some other number the program doesn’t do anything. The following flowchart would help you understand the flow of control in the program. 70.1
The previous post of the blog deals with Operators in C Programming.

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C Language Operators Associativity

When an expression contains two operators of equal priority the tie between them is settled using the associativity of the operators. Associativity can be of two types—Left to Right or Right to Left. Left to Right associativity means that the left operand must be unambiguous. It means it can not be involved in evaluation of any other sub-expression. Similarly, in case of Right to Left associativity the right operand must be unambiguous.

Let us understand this with an example.

EX 1 : Consider the expression a = 3 / 2 * 5 ;

Here there is a tie between operators of same priority, that is between / and *. This tie is settled using the associativity of / and *. But both enjoy Left to Right associativity. The following diagram shows for each operator which operand is unambiguous and which is not.


Since both / and * have L to R associativity and only / has unambiguous left operand (necessary condition for L to R associativity) it is performed earlier.

EX 2 : Consider one more expression a = b = 3 ;

Here both assignment operators have the same priority and same associativity (Right to Left). The following Figure shows for each operator which operand is unambiguous and which is not.


Since both = have R to L associativity and only the second = has unambiguous right operand (necessary condition for R to L associativity) the second = is performed earlier.

EX 3 : Consider yet another expression z = a * b + c / d ;

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Here * and / enjoys same priority and same associativity (Left to Right). The below Figure shows for each operator which operand is unambiguous and which is not.


Here since left operands for both operators are unambiguous Compiler is free to perform * or / operation as per its convenience since no matter which is performed earlier the result would be same.
54.1

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Priority of Arthematic Operations in C Language Programming

The previous post of the blog about c programming deals with concept of mathematical conversions.

The priority or precedence in which the operations in an arithmetic statement are performed is called the hierarchy of operations. The hierarchy of commonly used operators is shown in Figure .

General rules :

1 . Within parentheses the same hierarchy as mentioned in Figure 1.11 is operative. Also, if there are more than one set of parentheses, the operations within the innermost parentheses would be performed first, followed by the operations within the second innermost pair and so on.

2 . We must always remember to use pairs of parentheses. A careless imbalance of the right and left parentheses is a common error. Best way to avoid this error is to type ( ) and then type an expression inside it.

Examples :

1 . Determine the hierarchy of operations and evaluate the following expression:

i = 2 * 3 / 4 + 4 / 4 + 8 - 2 + 5 / 8

This can be done step by step as shown.

i = 6 / 4 + 4 / 4 + 8 - 2 + 5 / 8 operation: *
i = 1 + 4 / 4 + 8 - 2 + 5 / 8 operation: /
i = 1 + 1+ 8 - 2 + 5 / 8 operation: /
i = 1 + 1 + 8 - 2 + 0 operation: /
i = 2 + 8 - 2 + 0 operation: +
i = 10 - 2 + 0 operation: +
i = 8 + 0 operation : -
i = 8 operation: +

Note that 6 / 4 gives 1 and not 1.5. This so happens because 6 and 4 both are integers and therefore would evaluate to only an integer constant. Similarly 5 / 8 evaluates to zero, since 5 and 8 are integer constants and hence must return an integer value.

2 . Determine the hierarchy of operations and evaluate the following expression:

k = 3 / 2 * 4 + 3 / 8 + 3

Stepwise evaluation of this expression is shown below:

k = 3 / 2 * 4 + 3 / 8 + 3
k = 1 * 4 + 3 / 8 + 3 operation: /
k = 4 + 3 / 8 + 3 operation: *
k = 4 + 0 + 3 operation: /
k = 4 + 3 operation: +
k = 7 operation: +

All operators in C are ranked according to their precedence.

conversion of a general arithmetic statement to a C statement :

Here is the list of some simple examples which will give a outline about the conversion .


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C Program Conversion of constants

We have learned regarding C Program arithmetic instructions in the previous post.Here we are going to discuss regarding Integer and Float Conversions first.

Rules of implicit conversion of floating point and integer values in C :

1 . An arithmetic operation between an integer and integer always yields an integer result.

2 . An operation between a real and real always yields a real result.

3. An operation between an integer and real always yields a real result. In this operation the integer is first promoted to a real and then the operation is performed. Hence the result is real.

Examples :


Type Conversion in Assignments :

It may so happen that the type of the expression and the type of the variable on the left-hand side of the assignment operator may not be same.In such a case the value of the expression is promoted or demoted depending on the type of the variable on left-hand side of = .

Example 1. :

int i ;
float b ;
i = 3.5 ;
b = 30 ;

Here in the first assignment statement though the expression’s value is a float (3.5) it cannot be stored in i since it is an int. In such a case the float is demoted to an int and then its value is stored. Hence what gets stored in i is 3. Exactly opposite happens in the next statement. Here, 30 is promoted to 30.000000 and then stored in b, since b being a float variable cannot hold anything except a float value.

Example 2. :

float a, b, c ; int s ; s = a * b * c / 100 + 32 / 4 - 3 * 1.1 ;

Here, in the assignment statement some operands are ints whereas others are floats. As we know, during evaluation of the expression the ints would be promoted to floats and the result of the expression would be a float. But when this float value is assigned to s it is again demoted to an int and then stored in s.
Example 3. :

Note that though the following statements give the same result, 0, the results are obtained differently.

k = 2 / 9 ; k = 2.0 / 9 ; In the first statement, since both 2 and 9 are integers, the result is an integer, i.e. 0. This 0 is then assigned to k.

In the second statement 9 is promoted to 9.0 and then the division is performed. Division yields 0.222222.

However, this cannot be stored in k, k being an int. Hence it gets demoted to 0 and then stored in k.
48.5

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c program Arithmetic Instruction

This part of lesson deals with c language programming instructions and its first part is published here.Here is the continuation for that.

A arithmetic statement could be of three types. These are as follows:

1 . Integer mode arithmetic statement This is an arithmetic statement in which all operands are either integer variables or integer constants.

Ex: int i, king, issac, noteit ;
i = i + 1 ;
king = issac * 234 + noteit - 7689 ;

2 . Real mode arithmetic statement This is an arithmetic statement in which all operands are either real constants or real variables.

Ex: float qbee, antink, si, prin, anoy, roi ;
qbee = antink + 23.123 / 4.5 * 0.3442 ;
si = prin * anoy * roi / 100.0 ;

3 . Mixed mode arithmetic statement This is an arithmetic statement in which some of the operands are integers and some of the operands are real.

Ex: float si, prin, anoy, roi, avg ;
int a, b, c, num ;
si = prin * anoy * roi / 100.0 ;
avg = ( a + b + c + num ) / 4 ;

Execution of an arithmetic statement : Firstly, the right hand side is evaluated using constants and the numerical values stored in the variable names. This value is then assigned to the variable on the left-hand side.

Note :

1 . C allows only one variable on left-hand side of =. That is, z = k * l is legal, whereas k * l = z is illegal.

2 . In addition to the division operator C also provides a modular division operator. This operator returns the remainder on dividing one integer with another. Thus the expression 10 / 2 yields 5, whereas, 10 % 2 yields 0. Note that the modulus operator (%) cannot be applied on a float. Also note that on using % the sign of the remainder is always same as the sign of the numerator. Thus –5 % 2 yields –1, whereas, 5 % -2 yields 1.

3 . An arithmetic instruction is often used for storing character constants in character variables.

char a, b, d ; a = 'F' ;
b = 'G' ; d = '+' ;

When we do this the ASCII values of the characters are stored in the variables. ASCII values are used to represent any character in memory. The ASCII values of ‘F’ and ‘G’ are 70 and 71.

4 . Arithmetic operations can be performed on ints, floats and chars.

Thus the statements,

char x, y ;
int z ; x = 'a' ;
y = 'b' ;
z = x + y ;

are perfectly valid, since the addition is performed on the ASCII values of the characters and not on characters themselves. The ASCII values of ‘a’ and ‘b’ are 97 and 98, and hence can definitely be added.

5 . No operator is assumed to be present. It must be written explicitly. In the following example, the multiplication operator after b must be explicitly written.

Ex:

a = c.d.b(xy) is the usual arithmetic statement and
b = c * d * b * ( x * y ) is the statement in C .

6. Unlike other high level languages, there is no operator for performing exponentiation operation.
Thus following statements are invalid.

a = 3 ** 2 ;
b = 3 ^ 2 ;

For exponentiation we shall follow the following process.

#include
main( )
{ int a ;
a = pow ( 3, 2 ) ;
printf ( “%d”, a ) ;
}

Here pow( ) function is a standard library function. It is being used to raise 3 to the power of 2. #include is a preprocessor directive. It is being used here to ensure that the pow( ) function works correctly.
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