CH03: Input/Output Functions and statements

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Escape Sequences

Escape sequences are control characters used to move the cursor and print characters such as ?, ", \ and so on.

Some escape sequences 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.
\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	Prints the character represented by the octal number.
\xhh	Hexadecimal escape sequence	Prints the character represented by the hexadecimal number.

Format Specifiers

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Format specifiers are used to specify the format of a variable or other while using input or output functions

Some format specifiers 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	Scientific notation	Prints or reads a floating-point number in scientific notation.
%g or %G	Compact float	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.
%%	Percent sign	Prints a literal percent sign.

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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.

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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.

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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.

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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