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

Operators

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

Looping

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

Functions

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

Scope

Scope C Local Scope C Global Scope

Storage Classes

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

Array

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

String

What is String C String Functions

Pointer

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

Structure

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

Union

What is Union

Files

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 Files

A file is a collection of related records stored in a secondary storage of the computer. These informations are stored permanently. C allows programmers to read and write to the files when required.

C Files

File Types in C

  • Text Files
  • Binary Files

C Text Files

A text file consisting of sequence of characters, numbers or contain sequence of lines. C provides library functions to access text files.

Binary Files

A Binary file consisting of collection of bytes.

Reading And Writing Into a File

Step 1: Before starts reading or writing into a file, programmers should declare a file pointer variable which points to a structure FILE. This helps to access file.

Syntax - File pointer declaration

Syntax
FILE *fptr;

The above syntax represent the FILE structure has the pointer variable *fptr. The file pointer is used to access the file.

Step 2: A file must be opened before the reading and writing operation begins. The function fopen() is the only function used to open a file.

C Opening Modes of Files

Mode Meaning Description
w Write Create a file for writing, if the file already exist, it will be used to overwrite a file.
r Read Opening a file for reading only
a Append Opening a file to writing at an end of file.
w+ Write + Read Opening a file for writing and reading
r+ Read + Write Opening a file for reading and writing
a+ Append + Read Opening a file to update or append information

Syntax - Open a File

Syntax
FILE *fptr ;
fptr = fopen("data.dat", "r");

The above syntax represents that the fopen() function will open the file data.dat in read mode. The function fopen checks the disk for a file(data.dat), if the file already exists, it will be opened for further read or write operation. Otherwise, it creates a new file.

Step 3: After completion of reading and writing operations, the file must be closed. C provides a special function fclose() to closing a file.

Syntax - Closing a File

Syntax
fclose(fptr);

C program - Files

files.c
#include <stdio.h>
int main()
{
FILE *fptr;
fptr = fopen("data.dat","r");
if(fptr == NULL)
printf("ERROR: Not able to open the file ");
else
fclose(fptr);
return 0;
}
  • ERROR: Not able to open the file

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