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C language learned by suffering
C language learned by suffering

Exercise 18

fundamental knowledge

What do you call a variable whose value does not change during the program?

Q 1-2
What do you call a simple function created using a replacement function?

program read-only
In the following program, what is the macro TRI for?
Answer judging from the processing contents and variable names.

 #include <stdio.h>

#define TRI(A, H) ((A) * (H) / 2)

int main(void)
    int side, high, square;

    scanf("%d,%d", &side, &high);
    printf("%d\n", TRI(side, high));

    return 0;

program writing

I created in Exercise 11, a
The program should display whether the Olympics will be held when the year of the year is entered.
However, the part of the program that calculates the date of the Olympics must be created as a separate function.
In addition, the return value of the function should be returned as an enum constant.

descriptive expression

You could just write the number directly or use a variable, but you can't
Indirectly explain why you bother to use constants.

Basic Knowledge (sample answers)

Solution 1-1

Solution 1-2

Program reading (example solution)

Solution 2-1
Macro to find the area of a triangular shape.

Program writing (example of solution)

Solution 3-1
 #include <stdio.h>

int olympic(int year);

The enum {

int main(void)
    int year, hold;

    scanf("%d", &year);
    hold = olympic(year);

    switch (hold) {
    case OLYMIPC_NON:
        printf("not opened\n");
        printf("Summer Olympics\n");
        printf("Winter Olympics\n"); break; case OLYMIPC_WINTER: printf("Winter Olympics\n")

    return 0;

int olympic(int year)
    if (year % 2 == 0) {
        if (year % 4 == 0) {
            return OLYMIPC_SUMMER;
        } else {
            return OLYMIPC_WINTER;
    } else {
        return OLYMIPC_NON;

*The name given to the state in which the event is held has been used to
It is easier to understand than to distinguish by a numerical value such as 0.1.2.
Short Answer Type (Sample Answer)

Solution 4-1
Naming them makes them easier to understand and prepare changes.
Furthermore, constants are not assignable, so the values cannot be changed by mistake, leading to the phenomenon of bugs.

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 Partition
  3. Exercise 20


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