Parsing numeric arguments - Cheat Sheet & Quick Revision

Recall & Review

beginner

What function in C is commonly used to convert a string to an integer?

The atoi() function converts a string to an integer. It reads the string until it finds a non-numeric character.

intermediate

What is the difference between atoi() and strtol()?

atoi() converts a string to an int but does not handle errors well. strtol() converts to long int and provides error checking by using an end pointer and errno.

intermediate

How can you check if a numeric argument is valid when parsing a string in C?

Use strtol() with an end pointer. If the end pointer points to the string's end, the whole string was a valid number. Also check errno for overflow or underflow.

beginner

What header file must be included to use strtol()?

Include <stdlib.h> to use strtol().

intermediate

Why is it important to check the base parameter in strtol()?

The base parameter tells strtol() which number system to use (e.g., 10 for decimal, 16 for hex). Using the wrong base can cause incorrect parsing.

Which function converts a string to a long integer and allows error checking?

A strtol()

B atoi()

C sprintf()

D strlen()

strtol() converts strings to long integers and provides error checking via an end pointer and errno.

What does atoi() return if the string does not start with a number?

A The first character

B -1

C An error code

D 0

atoi() returns 0 if the string does not start with a valid number.

Which header file is required to use strtol()?

A <stdio.h>

B <stdlib.h>

C <string.h>

D <math.h>

strtol() is declared in <stdlib.h>.

What does the 'endptr' argument in strtol() help you determine?

A Where the number parsing stopped

B The base of the number

C The length of the string

D The maximum value parsed

The 'endptr' points to the character after the last parsed digit, helping detect invalid characters.

If you want to parse a hexadecimal number string, what base should you pass to strtol()?

A 8

B 10

C 16

D 2

Use base 16 to parse hexadecimal numbers.

Explain how to safely parse a numeric argument from a string in C.

Think about how to detect invalid input and overflow.

Describe the limitations of using atoi() for parsing numbers.

Consider what happens if the input is not a number.