02. First C Program — Line by Line

main, include, printf, return — har line ka matlab + live practice

Learning goals:

#include kya karta hai
main kyun zaroori hai
printf se output
return 0 ka matlab

1. Program ka skeleton

Almost har beginner C program is shape me hota hai:

1) Library include karo (I/O ke liye)
2) main function likho — yahan se program start
3) Statements likho (jaise print)
4) return 0 — “sab theek raha”

2. Har hisse ka matlab

#include <cstdio> — standard input/output functions laata hai (printf, scanf).
int main() — entry point; int ka matlab function number return karega.
printf("...") — text output. \n = new line.
return 0; — success code OS ko.

Common mistake: semicolon ; bhoolna, ya quotes band na karna → error.

Live practice 1 — Hello with two lines

Dono lines print honi chahiye. Apna naam second line me likh ke Run karo.

#include <cstdio>

int main() {
    printf("Hello, world!\n");
    printf("Mera naam: Student\n");
    return 0;
}

Live practice 2 — Numbers bhi print

%d integer ke liye format specifier hai. Number badal ke dekho.

#include <cstdio>

int main() {
    printf("2 + 3 = %d\n", 2 + 3);
    printf("Year: %d\n", 2026);
    return 0;
}

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