Convert character code to character

The idea

Converting a character code to a character means taking an integer that represents a character in the computer's encoding and finding the character it stands for. This is the reverse of converting a character to its code. In many languages a built-in function performs this: in Python, chr(65) returns 'A' and chr(97) returns 'a'. The integer must be a valid code in the encoding being used, such as ASCII or Unicode, otherwise the result may be an unexpected or unprintable character. To answer a question on this, take the given integer, apply the encoding rule, and state the single character it represents. Remember that different codes give different characters, and that a code such as 55 represents the digit character '7', not the number 7. The operation produces one character at a time.

What earns the marks

• States that converting a character code to a character returns the character that the encoding represents with that integer.
• Identifies the correct character for a given code, for example that 65 gives 'A' in ASCII.
• Recognises that different codes give different characters, for example 65 gives 'A' and 97 gives 'a'.
• Distinguishes a code such as 55, which represents the digit character '7', from the numeric value 7.
• Names a typical built-in function that performs the conversion, such as chr() in Python.
• Explains that the code must be valid in the encoding used, otherwise the result may be unexpected or unprintable.

Common mistakes and how to put them right

• Assuming that the code 7 produces the character '7'.

  Put it right: The digit character '7' has code 55 in ASCII, while 7 is a different control code.

• Believing that 65 and 97 produce the same character.

  Put it right: 65 gives upper-case 'A' and 97 gives lower-case 'a'.

• Confusing the two directions of conversion.

  Put it right: Code-to-character uses a function such as chr(), while character-to-code uses a function such as ord().

Exam tips

• Learn the ASCII codes for a few anchor characters such as 65 for 'A' and 97 for 'a' so you can work out nearby characters.
• Check whether the given code falls in the upper-case or lower-case range before deciding the character.
• Confirm whether the question asks for code-to-character or character-to-code before selecting an answer.