C Library Functions: Low-Level Input/Output

Port Input/Output

Function Header File Description
_inp conio.h
builtin.h
Reads a byte value from a specified input port.
_inpd conio.h
builtin.h
Reads a 4-byte value from a specified input port.
_inpw conio.h
builtin.h
Reads a 2-byte value from a specified input port.
_outp conio.h
builtin.h
Writes a byte value to a specified output port.
_outpd conio.h
builtin.h
Writes a 4-byte value to a specified output port.
_outpw conio.h
builtin.h
Writes a 2-byte value to a specified output port.
umask io.h Sets the file permission mask of the executing process environment.

Character and String Input/Output

Function Header File Description
_cgets conio.h Reads a string from the keyboard into locations given by arguments.
_cprintf conio.h Formats and sends a series of characters and values to the screen.
_cputs conio.h Writes a string directly to the screen.
_cscanf conio.h Reads data from the keyboard into locations given by arguments.
_getch conio.h Reads a single character from the keyboard.
_getche conio.h Reads a single character from the keyboard and displays it.
_kbhit conio.h Tests if a key has been pressed on the keyboard.
_putch conio.h Writes a character to the screen.
_ungetch conio.h Pushes a character back to the keyboard.

Direct Input/Output

Function Header File Description
read io.h Reads bytes from a file into a buffer.
write io.h Writes bytes from a buffer into a file.

File Positioning

Function Header File Description
__eof io.h Determines whether the file pointer has reached the end of the file.
_tell io.h Gets the current position of a file pointer.

File Access

Function Header File Description
access io.h Determines whether the given file exists and whether you can gain access to it.
chmod io.h Changes the permission setting of a file.
close io.h Closes a file associated with the handle.
creat io.h Creates a new file or opens and truncates an existing file.
dup io.h Associates a second file handle with an open file.
dup2 io.h Associates a second file handle, with possibly different attributes, with an open file.
isatty io.h Determines whether the handle is associated with a character device.
open io.h Opens a file and prepares it for subsequent reading and writing.
_sopen io.h Opens a file and prepares it for subsequent shared reading or writing.

File Operations

Function Header File Description
_chsize io.h Lengthens or cuts off the file to a specified length.
_filelength io.h Returns the length of a file.


Alphabetical Listing of IBM C and C++ Compilers Functions and Macros