Manipulating File IO in Visual C

1
Manipulating File IO in Visual C

• Speaker Yao-Ting Huang
• Advisor Kun-Mao Chao

National Taiwan University Department of Computer
Science Information Engineering Algorithms and
Computational Biology Lab.
2
Standard IO Manipulating Functions

• You have to include ltstdio.hgt.
• You have to use the file pointer.
• include ltstdio.hgtFile fpfp
  fopen(myfile.txt, w)
• fprintf(fp,Hello!)
• fclose(fp)
• The fopen function requests OS for a memory
  buffer.
• Your program actually reads/writes to the buffer,
  and the OS controls the trasmission between the
  buffer and disk.

3
Standard IO Manipulating Functions

• The fclose function flushes the remaining
  contents in the buffer and release the pointer
  and buffer.
• The maximum number of opened file pointers are
  depending on OS.

Write
Write
Disk
Memory Buffer
C Program
Read
Read
4
Standard IO Manipulating Functions

• The syntax of fopen
• File fopen(char filename, char mode)
• mode r, w, a, r, wb, etc.
• If the file can not be open or created, the fopen
  function returns 0 (NULL).
• Other file manipulating functions
• fscanf and fprintf formatted input/output file
  functions.
• fgetc, fputc get or put a single char from or
  into a file.
• fgets, fputs get or out a string from or into a
  file.
• See an example.

5
Homework 4 (1/3)

• Write a program that prompts the user to input an
  integer n.
• Draw a triangle with n levels, and each level has
  n star symbols. For example,
• n 3,
• After drawing the triangle, repeat the above
  process until the user inputs a negative integer.

6
Homework 4 (2/3)

• An usage scenario
• Please input 2 Please input 3
  Please input -9Thank you for using this
  program.

7
Homework 4 (3/3)

• You can draw other shapes to get bonus.
• e.g., n3 (triangle)
• e.g., n3 (reverse triangle)
  
• Due date 11/18.

8
Outline of Lecture Today

• A C file application.
• Demo of your Homework 3.
• Please make sure your program is ready to execute.