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Session 2 Loops and Control flow in CA COMPLETE C PROGRAMMING SERIES FROM BASICS TO ADVANCED

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Looping Constructs• Executing a set of statements repeatedly until a specified condition

is satisfied. The segment of code executed repeatedly is termed as a Loop.o while - loopo for - loopo do – while loop

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while Loop - Syntax

Initialization step;

while (condition)

{

Statements to be repeated;

Re-Initialization Step;

}

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While Loop Flow

Diagram

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for Loop - Syntax

for ( Initialization step; conditional step; re-initialization step )

{

Statements to be repeated;

}

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Flow Diagram for loop

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do-while Loop - Syntax

Initialization step;

do

{

Statements to be repeated;

Re-Initialization Step;

} while (condition);

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Flow Diagram do-while loop

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break & continue statements in loop constructs

• When a break statement is encountered inside a loop, the loop is terminated and control passes to the statement following the loop body.

• The continue statement forces the next iteration of the loop to take place, skipping any code following the continue statement in the loop body.

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Break statement

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continue statement

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exit ()

• Is a library function which terminates the execution of the program itself.

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goto statement

• It allows us to push the program control to any statement in the program.

goto <label-name>; where, label-name with a colon is used somewhere in the program.

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Arrays

• Storing a collection of elements of homogenous data type in contiguous memory locations referenced by a single name.

• Individual items in array can be referred to by an array name and a subscript or index.

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Array Memory Map

4 Bytes for Integer With some Starting Address say “a” (let it be 100)

Address will be a+4 (if a is 100 it will be 116)

Value will be *(a+4) or a[4] or 4[a] or *(4+a)

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Array handling in C Array declaration :-int i[5];

Array initialization :-static int i[5] = {1, 2, 3, 4, 5};

Entering Data into Array :-i[3] = 10;

Reading data from Array :-j = i[3];

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Complete Program using Arrays

void main()

{

int i[5], j;for (j=0; j<5; j++)

i[ j ] = j+1;for (j=0; j<5; j++)

printf ( “%d”, i[ j ]); }

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Some facts about Arrays in C

• Array elements are given garbage values till initialized.• Bounds checking is not taken care of regarding arrays in C.

Hence, this issue becomes the botheration of the programmer.• String constant is a one-dimensional array of characters

terminated by null.

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Two Dimensional Arrays Referred as a Matrix. Array declaration :-int i [5] [3]; 5 by 3 2-D matrix

Array initialization :-static int i [5] [2] = { {1, 2, 3, 4, 5}, {6, 7, 8, 9, 0}};

Entering Data into Array :-i[3][4] = 20;

Reading data from Array :-j = i[3][4];

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Two dimensional

Arrays

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Modular Programming• A long continuous program is breaked up into a series of individual

modules.• All these modules are related to each other in a specified fashion.• Called as sub-programs or functions.

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Functions in C• A function is a self-contained block of code performing a coherent

task of some kind.• Any C program contains at least one function – main(). • All other functions are called from main() itself.

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Function declaration and Function definition• Function declaration specifies the interpretation & attributes of a set of

identifiers. It alludes to a function that is defined elsewhere in the program. void abc ( int a );

• Function definition defines what function does as well as the kind of data it expects & returns.

void abc ( int a ) Function Header

{

… Function Body

}

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The Function Headerint AddNum(int a, int b)• This is the first line of the function. It consists of 3 parts :

◦ The type of the return value.◦ The name of the function.◦ The parameters of the function.

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The Function Body• The statements in the Function Body perform the desired

computation in a function body following the function header.• All the variables declared within the body of the function, as well as

the parameters are local to the function.

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Functions with Arguments• Mechanism to convey information to called functions from caller

functions. void abc ( int a ) ; Called Function

void main( ) Caller Function { a is a formal argument

int b = 10; abc (b); b is an actual argument

}

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End of

Session 02