Changing the Flow of the Program

As we have seen so far, the default execution flow (the order in which the code is executed) is sequential. This means that the code runs from top to bottom.

We can change the execution flow of the program by using constructs (control structures). There are two types of constructs:

• Conditional constructs
• Iterative constructs

Conditional constructs

These are used to execute sections of code when certain conditions are fulfilled. There are 3 conditional constructs in C:

• if statement

if (condition){
    do something;
}

• if-else statement

if (condition){
    do this when condition is fulfilled;
}else{
    do this when condition is not fulfilled;
}

• switch-case statement

switch (variable){
    case first_case:
        do something;
        break;
    case second_case;
        do something_else;
        break;
    default:
        do default_action;
}

Iterative constructs

These are used to execute sections of code multiple times. There are 3 conditional constructs in C:

• for

for (int i=0;i<n;i++){
    something to do n times;
}

• while loop

while (condition){
    do this as long as condition is fulfilled;
}

• do-while loop

do {
    do this as long as condition is fulfilled;
} while (condition);