getchar() & putchar()

getchar() and putchar(), both declared in <stdio.h>, are the simplest character-level I/O functions in C. getchar() reads a single character from standard input, and putchar() writes a single character to standard output. Together they are the building blocks for processing text one character at a time.

#include <stdio.h>

int main(void) {
    printf("Type a character: ");
    int c = getchar();

    printf("You typed: ");
    putchar(c);
    putchar('\n');
    return 0;
}

getchar() Returns int, Not char

This matters for correctly detecting EOF

getchar() is declared to return an int, not a char. This is deliberate: it needs to represent every possible unsigned char value plus one extra, distinct value, EOF (typically -1), to signal end-of-input or an error. If you store the result in a plain char variable, on platforms where char is unsigned, a legitimate character value could be mistaken for EOF, or EOF itself could get truncated into a valid-looking character — breaking the end-of-input check entirely. Always store the result in an int.

char c = getchar();       // BUG RISK: narrowing to char can corrupt the EOF check
if (c == EOF) { /* may never trigger correctly on some platforms */ }

int cCorrect = getchar(); // CORRECT: int can hold every char value plus EOF
if (cCorrect == EOF) { /* reliable */ }

The Classic Read-Until-EOF Loop

A very common C pattern reads characters one at a time until EOF is reached, doing some work with each character along the way.

#include <stdio.h>

int main(void) {
    int c;
    int count = 0;

    while ((c = getchar()) != EOF) {
        putchar(c);   // echo the character back out
        count++;
    }

    printf("\nRead %d characters\n", count);
    return 0;
}

Note

The assignment (c = getchar()) inside the loop condition is a deliberate, idiomatic use of assignment-as-expression: it reads one character, stores it in c, and the whole expression evaluates to that same value for the != EOF comparison. The parentheses are required — without them, c = getchar() != EOF would first compare getchar() to EOF and then assign the boolean result (0 or 1) to c, which is not what you want.

getchar() reads one character from stdin; putchar() writes one character to stdout
getchar() returns int, not char, specifically so it can represent EOF unambiguously
Always store the result of getchar() in an int variable, never a plain char
while ((c = getchar()) != EOF) is the standard idiom for processing input one character at a time