05. Input & Output

printf formats, scanf, stdin box se live input

Goals:

printf format mastery
scanf se input
Live stdin box use karna

1. printf — output

Format string me placeholders:
%d int · %f float · %c char · %s string · \n newline

2. scanf — input

scanf("%d", &n) — user se number padho, n me store.
& zaroori hai: “n ka address do taaki value wahan likh saku”.

Is page pe Program input box = stdin (jaise keyboard).

Live practice 1 — Number input

Neeche input box me ek number likho (default 42), phir Run.

Program input (stdin)

#include <cstdio>

int main() {
    int n;
    printf("Enter number: ");
    if (scanf("%d", &n) == 1) {
        printf("\nYou entered %d\n", n);
        printf("Double = %d\n", n * 2);
    } else {
        printf("\nInvalid input\n");
    }
    return 0;
}

Real C tip: hamesha scanf ka return check karo — galat input pe program crash/ weird values se bachoge.

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