ASCII and UTF-8
- C course
- Advanced
- Lesson 61/83
- 5 min
Learn the difference between ASCII and UTF-8.
ASCII and UTF-8
ASCII is a 7-bit table from 0-127; each letter is one byte. UTF-8 is Unicode's variable-length encoding: ASCII characters are one byte, non-Latin characters are 2-4 bytes.
In C, char is one byte and strlen counts bytes; so strlen("Merhaba") returns 7 while strlen("çağ") returns 5 ('ç' and 'ğ' are two bytes each). The ASCII value of 'A' is 65. The difference between byte count and character count is the essence of UTF-8.
Counting bytes
To print the ASCII value of 'A' you write printf("%d", 'A');; this prints 65. strlen gives the byte count of a string.
Example: strlen("Merhaba") returns 7; 'M', 'e', 'r', 'h', 'a', 'b', 'a' are seven bytes. For a pure ASCII string the byte count equals the character count. This fact is the basis of UTF-8 handling: you first get the byte count, then decode characters.
Practice ASCII value and byte count
Print the ASCII value of 'A' with printf("ASCII: %d\n", 'A');. Print the byte count of the string with printf("bayt: %zu\n", strlen("Merhaba"));. Don't forget <string.h>.
Starter code
#include <stdio.h>
#include <string.h>
// Print ASCII value of 'A' with %d
// Print byte count of "Merhaba" with strlen
int main(void) {
return 0;
}Sample solution
#include <stdio.h>
#include <string.h>
int main(void) {
printf("ASCII: %d\n", 'A');
printf("bayt: %zu\n", strlen("Merhaba"));
return 0;
}Expected output
ASCII: 65 bayt: 7
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 How many bytes is the letter 'ü' in UTF-8?
- 2 Correct answer
- 1
- 3
- 4
Explanation: 'ü' is a non-Latin letter, so it is 2 bytes in UTF-8.
2 Find the string length
int n = strlen("____");int n = strlen("Merhaba");Explanation: strlen("Merhaba") returns 7.
3 Match the concepts
| Term | Meaning |
|---|---|
ASCII |
7-bit 0-127 |
UTF-8 |
Variable length |
char |
Single byte |
strlen |
Counts bytes |