🚀 0. Programming from Zero

0.1 What is a Problem?

A problem is a situation where we know some information, need a particular result, and must find a method to reach that result.

0.2 How Do We Normally Solve a Problem?

For a small problem, you may find the answer in your head. To program the solution, write down the comparisons or calculations you used so that the same method works with other inputs.

0.3 What is Programming?

0.4 Why Do We Need a Programming Language?

You can describe an idea in English or Telugu, but a C program must follow C’s rules. A compiler translates that source into a form that can be linked and run on the target system.

0.5 The Basic Input–Process–Output Idea

Many programming problems become easier when you first identify three things: Input, Process, and Output.

0.6 What is an Algorithm?

0.7 Characteristics of a Good Algorithm

0.8 What is a Flowchart?

0.9 What is Pseudocode?

0.10 From Problem to C Program — Add Two Numbers

BEGIN
    READ A, B
    SUM ← A + B
    PRINT SUM
END

#include <stdio.h>

int main()
{
    int a, b, sum;

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

    sum = a + b;

    printf("%d", sum);

    return 0;
}

0.11 Decision Making — Certificate Eligibility

BEGIN
    READ MARKS

    IF MARKS >= 40
        PRINT "Eligible"
    ELSE
        PRINT "Not Eligible"
    END IF
END

#include <stdio.h>

int main()
{
    int marks;

    scanf("%d", &marks);

    if(marks >= 40)
        printf("Eligible");
    else
        printf("Not Eligible");

    return 0;
}

0.12 Repetition — Print Numbers from 1 to 5

Suppose you need to print the numbers 1 to 5. You could write five separate print statements, but the action is repetitive. Programming gives us a better idea: repeat the same type of instruction using a loop.

print 1
print 2
print 3
print 4
print 5

SET i ← 1
WHILE i ≤ 5
    PRINT i
    i ← i + 1
END WHILE

BEGIN
    FOR i ← 1 TO 5
        PRINT i
    END FOR
END

#include <stdio.h>

int main()
{
    for(int i = 1; i <= 5; i++)
        printf("%d ", i);

    return 0;
}

0.13 Algorithm vs Flowchart vs Pseudocode vs Program

0.14 How to Think Before Writing Code

Before typing C statements, solve one small example on paper. Then answer these questions to check that the input, result, and steps are clear.

0.15 What is a Dry Run or Program Tracing?

A dry run means executing the logic manually using sample values. You track how variables change one step at a time before or while checking the program.

A = 10
B = 20

SUM = A + B
SUM = 10 + 20
SUM = 30

Output = 30

0.16 What if the Program Does Not Work?

Finding and correcting such problems is called debugging. Errors are a normal part of programming practice.

0.17 A Simple Problem-Solving Strategy

0.18 Common Beginner Mistakes

0.19 Mini Problem-Solving Practice

For each problem, first identify the Input, Output, and the main logic. Try it yourself before opening the answer.

0.20 Are You Ready to Start C?

You are ready for the next page when these ideas feel understandable. You do not need to be perfect yet.

#include <stdio.h>

int isPositive(int n)
{
    return n > 0;
}

int main(void)
{
    int test[] = {7, 0, -3};
    for (int i = 0; i < 3; ++i)
        printf("%d: %s\n", test[i],
               isPositive(test[i]) ? "positive" : "not positive");
    return 0;
}

7: positive
0: not positive
-3: not positive

0.22 Key Takeaway