CH03 : Input/Output Functions and statements

stdio.h stands for standard input-output header , we will be learning to use the functions present in this header file.

escape sequences # `Escape sequence are control characters used to move the cursor and print characters such as ?,",\ and so on.`
Some escape sequence are : | Escape Sequence | Description | Function | | --------------- | ------------------------------------------------------------ | ------------------------------------------------------------ | | `\n` | Newline (line feed) | Moves the cursor to the beginning of the next line. | | `\t` | Horizontal tab | Moves the cursor to the next tab stop. | | `\b` | Backspace | Moves the cursor back one position. | | `\r` | Carriage return | Moves the cursor to the beginning of the current line. | | `\f` | Form feed (page break) | Moves the cursor to the beginning of the next page. | | `\0` | Null Character | Represents the null character, which is the character with the ASCII value of 0. It is used to mark the end of a string and can be used for various other purposes, such as string manipulation and memory management. | | `\v` | Vertical tab | Moves the cursor down to the next vertical tab stop. | | `\a` | Alert (bell) | Produces an audible alert (usually a beep). | | `\\` | Backslash | Prints a backslash character. | | `\?` | Question mark | Prints a question mark. | | `\'` | Single quote | Prints a single quote. | | `\"` | Double quote | Prints a double quote. | | `\ooo` | Octal escape sequence (where `ooo` is an octal number) | Prints the character represented by the octal number. | | `\xhh` | Hexadecimal escape sequence (where `hh` is a hex number) | Prints the character represented by the hexadecimal number. |
format specifiers --- `Format specifier are used to specify the format of a variable or other while using input or output functions`
Some format specifier are :
| Format Specifier | Description | Function | | ---------------- | ------------------------------------------------------------ | ------------------------------------------------------------ | | `%d` or `%i` | Signed integer | Prints or reads a signed integer value. | | `%u` | Unsigned integer | Prints or reads an unsigned integer value. | | `%f` | Floating-point number | Prints or reads a floating-point number. | | `%e` or `%E` | Floating-point number in scientific notation | Prints or reads a floating-point number in scientific notation. | | `%g` or `%G` | Floating-point number in the more compact of `%f` or `%e` | Prints or reads a floating-point number in the more compact of `%f` or `%e`. | | `%c` | Single character | Prints or reads a single character. | | `%s` | String | Prints or reads a string. | | `%p` | Pointer | Prints the address of a pointer. | | `%x` or `%X` | Hexadecimal integer | Prints or reads a hexadecimal integer value. | | `%o` | Octal integer | Prints or reads an octal integer value. | | `%%` | Literal percent sign | Prints a literal percent sign.

printf() function

The printf() function is used in C programming to print or display information on the screen (monitor).

What it Does:

It shows the values of variables or text messages on the screen.

Syntax:

printf("format string", variable1, variable2, ..., variableN);

“format string”: Tells the computer how to display the values (like %d for integer, %f for float, etc.).

variable1, variable2, etc.: These are the variables whose values you want to display.

Examples:

float s = 2.8;
int k = 5, kfact = 120;

printf("%f", s);                          // Output: 2.800000
printf("\nsum = %6.2f", s);               // Output: sum =  2.80
printf("\n%d factorial is %d", k, kfact); // Output: 5 factorial is 120

scanf() function

The scanf() function is used to get input from the user through the keyboard.

What it Does:

It allows the user to enter values, which are stored into variables.

Syntax:

scanf("format string", &variable1, &variable2, ..., &variableN);

“format string”: Tells the computer what type of data to expect (%d for int, %f for float, etc.).

&variable: The & symbol means “address of” the variable. It tells the computer where to store the value entered by the user.

Examples:

int a, b;
float x;
char gender;
char sname[20];


scanf("%d %d", &a, &b);    // User enters two integers
scanf("%f", &x);           // User enters a float number
scanf("%c", &gender);      // User enters a character
scanf("%s", sname);        // User enters a string (one word)

MORE FUNCTIONS :

This guide covers common I/O functions in C from stdio.h and conio.h, with syntax and explanations.

Standard I/O Functions (<stdio.h>)

Function Syntax Explanation
getchar() char c = getchar(); Can take input of a character by reading one character from the keyboard when the user presses Enter. The character is stored in the variable (e.g., c).
putchar() putchar(c); Prints a single character to the screen. The character c must be provided.
gets() gets(buffer); Can take input of the user by reading a whole line of text (until Enter) from the keyboard and stores it in the variable buffer.
puts() puts(string); Prints the string to the screen and automatically moves the cursor to the next line.

Console I/O Functions (<conio.h> - Non-standard)

Function Syntax Explanation
getch() char c = getch(); Reads a single character from the keyboard without waiting for Enter. The character is not shown on the screen as it’s typed (useful for passwords).
getche() char c = getche(); Same as getch(), but echoes/print the character on the screen as the user types it.
putch() putch(c); Prints a single character to the screen, just like putchar(), but it’s from <conio.h>.
clrscr() clrscr(); Clears the console screen. Only works in old compilers like Turbo C/C++, not supported in modern IDEs like Code::Blocks or GCC.

Summary Table

Function What It Does Header File
getchar() Reads one char from user stdio.h
putchar() Outputs one char to screen stdio.h
gets() Reads a line of text stdio.h
puts() Prints a string with newline stdio.h
getch() Reads char instantly without showing it conio.h
getche() Reads char instantly and shows it on screen conio.h
putch() Outputs one char (same as putchar()) conio.h
clrscr() Clears screen (console window) conio.h

Table of contents