Final answer:
In C programming, flags like -std=c99, -Wall, and -pedantic are often required for strict adherence to C standards and receiving helpful compiler warnings. The -ansi flag is equivalent to -std=c89, both refer to the ANSI C standard.
Step-by-step explanation:
The flags mentioned are used in C programming to control the compilation process. Flags -std=c99 and -std=c89 specify the version of the C standard to which the code should conform. Flag -Wall enables all the compiler's warning messages which is useful for catching potential errors. The flag -pedantic is used to ensure strict ISO compliance, rejecting any code that isn't strictly standard C. The flag -ansi is synonymous with -std=c89, which both enforce the ANSI C standard, also known as C90. Lastly, the flag -w suppresses all warnings, which is generally not recommended, as warnings can indicate potential issues with the code.