sizeof vs strlen in C: Key Differences

Sizeof and strlen are two commonly used functions in the C language with different purposes, the main differences are as follows:

1. Sizeof is an operator, not a function, used to determine the byte size of a data type or variable. For example, sizeof(int) will return 4, indicating that an int type occupies 4 bytes of space, while sizeof(array) will return the total space occupied by the entire array. Sizeof performs its calculations during compile time, not at runtime.
2. The function strlen is used to calculate the length of a string, which is the number of characters in the string (excluding the \0 character at the end of the string). For example, strlen(“hello”) will return 5 because the string “hello” has 5 characters. strlen calculates at runtime and requires traversing the entire string until it encounters the \0 character at the end of the string.