C language file operation

• What is a document
• file name
• file type
• File buffer
• The file pointer
• Opening and closing of files
• Sequential reading and writing of files
• Random reading and writing of documents
• Determination of end of document

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What is a document

​ The files on disk are files .

But in programming , There are two kinds of documents we usually talk about ： Program files 、 Data files ​​

Program files

• ​ Include source files （ The suffix is .c）, Target file （windows Environment suffix is .obj）, Executable program （windows Environment suffix is .exe）.

Data files

• ​ The content of the file is not necessarily a program , It's the data that the program reads and writes when it runs , For example, the file from which the program needs to read data , Or output content file .

This chapter discusses data files .

In the previous chapters, the input and output of the processed data are targeted at the terminal , That is, input data from the keyboard of the terminal , The operation results are displayed on the display .

In fact, sometimes we output information to disk , When necessary, read the data from the disk to the memory for use , What we are dealing with here is the files on the disk .

file name

​ A file should have a unique file ID , So that users can identify and reference .

The filename contains 3 part ： File path + File name trunk + file extension

for example ： c:\code\test.txt

For convenience , Document identification is often referred to as file name .​

file type

​ According to the organization of data , Data files are called text file perhaps Binary .

Data is stored in memory in binary form , If the output without conversion is to external memory , Namely Binary .

​ If it's required to use ASCII In the form of code , You need to convert before storing . With ASCII The file stored in the form of characters is text file .

How is a data stored in memory ？

All characters are written in ASCII stored , Numerical data can be used either ASCII stored , It can also be stored in binary form .

If there are integers 10000, If the ASCII Code output to disk , The disk is occupied by 5 Bytes （ One byte per character ）, And binary form input Out , On the disk 4 Bytes （VS2013 test ）.​​