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C language learned by suffering
C language learned by suffering

Exercise 17

fundamental knowledge

What do you call a file in which only textual information is written?

Q 1-2
A file in which only numerical values are written
What do you call it in particular to distinguish it from the above files?

program read-only
When the following program is executed, what values will be written to what named file and in what format?

 #include <stdio.h>

int main(void)
    FILE* fp;
    int dat[3] = { 10, 20, 30 }

    fp = fopen("file.dat", "wb");
    fwrite(&dat, sizeof(dat), 1, fp);

    return 0;

program writing

number Name Average test score
1 Nobi Nobita 0
2 source silence 90
3 Takeshi Tsuyoda 40
4 Suneo Bonegawa 7

Create a program to create the above table in a format that can be opened in Excel.
Hint: CSV format can be opened in any spreadsheet software.

descriptive expression

Information that should just be displayed on the display
Briefly explain why you bother to file.

Basic Knowledge (sample answers)

Solution 1-1
text file

Solution 1-2
binary file

Program reading (example solution)

Solution 2-1
The values 10, 20, and 30 are written in binary format to the file.dat file.

Program writing (example of solution)

Solution 3-1
 #include <stdio.h>

int main(void)
    FILE* fp;

    fp = fopen("test.csv", "w");

    fprintf(fp, "number,name,average test score\n");
    fprintf(fp, "1,Nobita Nobi,0\n");
    fprintf(fp, "2,Minamoto Shizuka,90\n");
    fprintf(fp, "3,Takeshi Gouda,40\n");
    fprintf(fp, "4,Suneo Konekawa,70,\n");


    return 0;

*In this case, it is specified with a string literal, but if you are using an array or structure, even better.
*Points shall be deducted if the fclose function is forgotten.
Short Answer Type (Sample Answers)

Solution 4-1
Information on the screen disappears quickly, but
If it is a file, it can be stored semi-permanently and can be easily edited and passed on.

About this Site

The C language (bitter C), which is learned by suffering, is
This is the definitive C language introductory site.
It systematically explains the basic functions of the C language and
It is as complete as or more complete than any book on the market.

Part 0: Program Overview
  1. What is the program?
Chapter 2: How to write a program
  1. Writing Rules
  2. Writing conventions
  3. Exercise 2
Chapter 3: Display on Screen
  1. String display
  2. newline character
  3. Exercise 3
Chapter 4: Numeric Display and Calculation
  1. Numeric Display
  2. Basic Calculations
  3. Type of value
  4. Exercise 4
Chapter 5: Numerical Memory and Calculation
  1. Memorize values
  2. Variable Type
  3. Type conversion
  4. Numeric justification
  5. Exercise 5
Chapter 6: Input from the keyboard
  1. Functions for input
  2. Fear of Input
  3. Exercise 6
Chapter 9: Repetition with a fixed number of times
  1. Sentences that repeat themselves
  2. Loop Operation Mechanism
  3. Exercise 9
Chapter 10: Unknown number of repetitions
  1. Loop of unknown frequency
  2. input check
  3. Exercise 10
Chapter 13: Handling Multiple Variables at Once
  1. Multiple variables are handled together.
  2. How to use arrays
  3. Exercise 13
Chapter 19: Dynamic Arrays
  1. Create arrays at will
  2. Exercise 19
Chapter 20: Multiple Source Files
  1. Minimal division
  2. The Stone of Division
  3. Exercise 20


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