C Foundation

What is C? C Compiler Installation C Extensions C Compiler C Interpreter C Program Structure

C Basics

C Keywords C Data Types C Identifiers C Variables C Constant C Escape Sequences C Constant and Volatile C Typecast


What is Operator C Comma Operator C Arithmetic Operators C Relational Operators C Logical Operators C Bitwise Operators C Conditional Operators C : : Operator C Operator Priority

Basic IO's

Basic IO's C Formatted Functions C Unformatted Functions C Common Functions

Control Statements

What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement


What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop


What is Function C User Defined Functions C Recursion C Passing Parameters


Scope C Local Scope C Global Scope

Storage Classes

What is Storage Class C Auto C Extern C Static C Register


What is Array C One Dimensional Array C Two Dimensional Array C Multi Dimensional Array C Arrays Of Strings


What is String C String Functions


What is Pointer C Pointers Arithmetic C Pointer to Pointer C Pointers and Arrays C Pointers and Strings C Pointer to Functions Void Pointers Null Pointers C Null and Void Pointer


What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def


What is Union


What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

Memory Allocation

What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

C Reference

All ASCII Code Basic C Questions

C Interview

C Interview Sets All Star Patterns All Number Patterns All Alphabet Patterns All Series Patterns
The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Low level Disk IO

The Low level file IO is nothing but, the data is read or write to the file directly without the need of buffer. The Low level file IO functions use handles, so the data transfer speed is faster than high level IO functions. The following low level IO functions are defined in io.h header file.

Low level IO Functions

open() Function

The open() function is used to open a file. There are several modes to open a file.

Syntax - open()

open(filename, mode);
Open modes Meaning
O_CREATE opens a new file for writing
O_WRONLY open a file in write only mode
O_RDONLY open a file in read only mode
O_RDWR opens a file to read and write
O_APPEND open a file for appending
O_BINARY opens a file in a binary mode
O_TEXT used to create a text file
O_TRUNC opens a file for truncates a file

write() Function

The write() function is used to write data into a file.

Syntax - write()

write(int handle, void *buf, unsigned nbytes);

where, buf is the data area, nbytes referred as number of bytes to write into a file.

read() Function

The read() function is used to read from a file.

Syntax - read()

read(int handle, void *buf, unsigned nbytes);

close() Function

Syntax - close()

close(int handle);

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