Unit 2 – Algorithmic Approach

An algorithm is a step-by-step procedure to solve a problem. It must be clear, finite, and effective.

Characteristics of a Good Algorithm

• Input – Accepts zero or more inputs
• Output – Produces at least one result
• Definiteness – Steps are precise and unambiguous
• Finiteness – Must terminate after a finite number of steps
• Effectiveness – Each step is basic and executable

Example Algorithm: Find Sum of Two Numbers

1. Start
2. Read A and B
3. Compute Sum = A + B
4. Display Sum
5. End

Decision-making statements enable the program to choose different actions based on conditions.

3.1 The if Statement

if (condition) {
    // code to execute if true
}
            

3.2 if…else Statement

if (condition) {
    // true code
} else {
    // false code
}
            

3.3 Nested if Statements

if (a > 0) {
    if (a % 2 == 0) {
        printf("Positive Even");
    }
}
            

3.4 switch Statement

switch(choice) {
    case 1: printf("Option 1"); break;
    case 2: printf("Option 2"); break;
    default: printf("Invalid");
}
            

Control structures determine the flow of execution—whether instructions repeat, skip, or choose a path.

4.1 Looping Structures

• for loop – used when number of iterations is known
• while loop – repeats as long as the condition is true
• do…while loop – ensures the loop runs at least once

// for loop example
for (int i = 1; i <= 5; i++) {
    printf("%d ", i);
}

// while loop example
int i = 1;
while (i <= 5) {
    printf("%d ", i);
    i++;
}

// do-while example
int j = 1;
do {
    printf("%d ", j);
    j++;
} while (j <= 5);

4.2 Jump Statements

• break – exits a loop or switch
• continue – skips the current iteration
• goto – jumps to a labeled statement (generally avoided)

// break example
for (int i = 1; i <= 10; i++) {
    if (i == 5) break;
    printf("%d ", i);
}

#include 

int main() {
    int n;

    printf("Enter a number: ");
    scanf("%d", &n);

    if (n < 0) {
        printf("Negative number\n");
    } else if (n == 0) {
        printf("Zero\n");
    } else {
        printf("Positive number\n");
    }

    printf("Counting from 1 to %d:\n", n);
    for (int i = 1; i <= n; i++) {
        printf("%d ", i);
    }

    return 0;
}