Difference between "section" and "segment" in NASM

Question

I am using some baby NASM programs to help me learn the language.

From what I've read, NASM programs can have three sections; the .data, the .bss, and the .text which is mandatory. However I am finding very often that sometimes the names of the divisions are section and other times it's segment.

For example with this "Hello World" I found online:

;  hello.asm  a first program for nasm for Linux, Intel, gcc ; ; assemble: nasm -f elf -l hello.lst  hello.asm ; link:     gcc -o hello  hello.o ; run:          hello  ; output is:    Hello World       SECTION .data       ; data section msg:    db "Hello World",10 ; the string to print, 10=cr len:    equ $-msg       ; "$" means "here"                 ; len is a value, not an address      SECTION .text       ; code section         global main     ; make label available to linker  main:               ; standard  gcc  entry point      mov edx,len     ; arg3, length of string to print     mov ecx,msg     ; arg2, pointer to string     mov ebx,1       ; arg1, where to write, screen     mov eax,4       ; write sysout command to int 80 hex     int 0x80        ; interrupt 80 hex, call kernel      mov ebx,0       ; exit code, 0=normal     mov eax,1       ; exit command to kernel     int 0x80        ; interrupt 80 hex, call kernel 

If I change every instance of SECTION to SEGMENT it will still work.

Can someone explain the difference between the two, if any?

Answer 1

From the nasm documentation:

The SECTION directive (SEGMENT is an exactly equivalent synonym)

Nasm can produce output in various formats, some of which support sections. Certain section names can be arbitrary (such as the three you listed), for them only the section flags count. The predefined ones are just convenience shortcuts, .text is marked as containing code, .data as read-write initialized data and .bss as zero-initialized read-write data. You could put your code in a section named foo as long as it was marked as a code section, and you can use multiple sections as you see fit.