YouTipC Exercise Example10
## C Programming Exercise - Example 10: Printing Stairs with Smiley Faces
In this tutorial, you will learn how to use nested loops and extended ASCII characters in C to print a staircase pattern topped with two smiley faces. This exercise is excellent for mastering loop control structures and understanding character encoding in terminal outputs.
---
### Problem Description
Write a C program that prints a staircase pattern. At the very top of the stairs, the program should display two smiley faces.
---
### Algorithm Analysis
1. **Smiley Faces:** In the standard IBM PC Extended ASCII (Code Page 437) character set, the ASCII value `1` represents a white smiley face (`☺`). We can print this using the octal escape sequence `\1` or by casting the integer `1` to a character.
2. **Staircase Pattern:**
- We use nested `for` loops to control the rows and columns.
- The outer loop variable `i` controls the current row (representing the height of the stairs).
- The inner loop variable `j` controls the number of blocks printed in each row. The number of blocks in row `i` is proportional to `i`, creating a step-like pattern.
3. **Staircase Blocks:** The extended ASCII value `219` represents a solid block (`█`). Printing two of these blocks together (`%c%c`, 219, 219) creates a visually balanced square step.
---
### Code Implementation
Below is the complete C program to achieve this output.
```c
/**
* Description: Print a staircase pattern topped with two smiley faces.
* Website: YouTip (Classic C 100 Examples)
*/
#include
int main()
{
int i, j;
// Print two smiley faces using the ASCII value 1 (\1)
printf("\1\1\n");
// Outer loop controls the number of steps (10 rows)
for (i = 1; i < 11; i++)
{
// Inner loop controls the width of each step
for (j = 1; j <= i; j++)
{
// ASCII 219 represents a solid block character '█'
// Printing it twice makes the step look more like a square
printf("%c%c", 219, 219);
}
// Move to the next line after printing each step
printf("\n");
}
return 0;
}
```
---
### Expected Output
When compiled and run in an environment that supports Code Page 437 (OEM United States) encoding, the output will look like this:
```text
☺☺
██
████
██████
████████
██████████
████████████
██████████████
████████████████
██████████████████
████████████████████
```
---
### Important Considerations & Troubleshooting
#### 1. Garbled Characters or Question Marks (`?`) in the Output
If you see strange symbols, question marks, or raw numbers instead of smiley faces and solid blocks, it is because your modern terminal uses **UTF-8** encoding by default, whereas this program relies on the legacy **extended ASCII (Code Page 437)**.
**Solutions:**
* **On Windows (Command Prompt):**
Before running the compiled program, switch your active code page to OEM United States by executing the following command in your command prompt:
```cmd
chcp 437
```
* **Modern Cross-Platform Solution (Unicode/UTF-8):**
If you want your code to run natively on modern terminals (Linux, macOS, modern Windows Terminal) without changing system locales, you should use UTF-8 wide characters instead:
```c
#include
#include
int main() {
// Set the locale to use the system's default UTF-8 encoding
setlocale(LC_ALL, "");
// Print Unicode smiley faces (U+263A)
printf("\u263A\u263A\n");
for (int i = 1; i < 11; i++) {
for (int j = 1; j <= i; j++) {
// Print Unicode solid block (U+2588)
printf("\u2588\u2588");
}
printf("\n");
}
return 0;
}
```