What could cause a program in C not to be compiled??

Answer 1

Syntax errors. When your code doesn't follow syntax rules, it is unclear how it can be translated to machine code (=compiled)

Also missing imports or referencing undefined things (functions, variables etc)

Answer 2

Edirin deborah that is a separate question and i don't understand what you mean.
If urgently needed means that your homework assignment is due, please understand that we are not here to do that for you.
Anyway it seems to be super basic question, so i suggest you sit down and learn that stuff.

Answer 3

write the statement that receives a double value and save it in a variable identified number
please answer is urgently needed