Control Flow

Introduction

Control structures in C allow the programmer to control the flow of execution in a program. They are essential for decision-making, looping, and altering the sequence of instructions.

Control structures are broadly classified into three categories:

1. Conditional Control Structures

These structures help in decision-making by executing different code blocks based on certain conditions.

a) if, else if, else

• Executes a block of code if a condition is true.
• else if and else handle other conditions. Example:

int temp = 35;
if (temp > 40)
    printf("High temperature\n");
else if (temp > 30)
    printf("Moderate temperature\n");
else
    printf("Low temperature\n");

b) switch

• Used when a variable is compared against multiple constant values.

• Helps reduce the complexity of multiple if-else conditions.

Example:

int mode = 2;
switch (mode) {
    case 1: printf("Manual Mode\n"); break;
    case 2: printf("Auto Mode\n"); break;
    default: printf("Unknown Mode\n");
}

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2. Looping Control Structures

Loops are used to repeat a set of statements multiple times.

a) for loop

• Best suited for cases where the number of iterations is known beforehand. Example:

for (int i = 0; i < 5; i++) {
    printf("i = %d\n", i);
}

b) while loop

• Used when the number of iterations is not known in advance.
• Condition is checked before entering the loop. Example:

int i = 0;
while (i < 3) {
    printf("i = %d\n", i);
    i++;
}

c) do...while loop

• Similar to the while loop, but the body is executed at least once. Example:

int i = 0;
do {
    printf("i = %d\n", i);
    i++;
} while (i < 3);

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3. Branching (Jump) Statements

These statements are used to alter the normal flow of control in a program.

a) break

• Immediately exits from a loop or switch statement. Example:

for (int i = 0; i < 5; i++) {
    if (i == 3) break;
    printf("%d ", i);
}

b) continue

• Skips the current iteration and jumps to the next iteration of the loop. Example:

for (int i = 0; i < 5; i++) {
    if (i == 2) continue;
    printf("%d ", i);
}

c) goto

• Transfers control to a labeled statement in the program.
• Generally avoided, but sometimes used in low-level programming or error handling. Example:

int x = 1;
if (x)
    goto end;
 
printf("This will be skipped\n");
 
end:
printf("Reached end label\n");