A computer program is a set of detailed directions to the computer. The computer can only do one baby step at a time. There are many computer languages to use to write a program. The computer itself uses machine language, which is all 1's and 0's. Assembly language uses abbreviations for machine language code. High-level languages use words and expressions that look like algebra, which must be compiled or interpreted before the computer actually can use the program. 4th generation languages are used for database queries and are results oriented. Natural languages would sound like regular speech. We don't have that yet.
FORTRAN is a computer language that is especially good for scientific work. It makes writing equations easy.
COBOL has been used for a long time for business programs and main frame programs. It has a structure that is similar to English, which makes it easier for non-technical people.
C and C++ are languages that are widely used for programs.
BASIC started as a language used to learn how to program but proved to be useful for actual programs, too. There are many versions of BASIC for working with specific software, like Word Visual Basic for writing macros for Microsoft Word.
The process of creating a computer program should start with the end user. If there is no one who wants your program, why bother? A systems analyst can design the structure of the program once the goals are laid out. A programmer turns that design into actual commands. The language she uses will depend in part on how complicated the tasks are that the program must do. Then the end user tests the program out to see if it does the job and if it is easy to work with. If it's not right yet, there is another round of design, programming, and testing. Round and round they go until everyone is satisfied. At least that's the way it should happen.
During program development, it is important to document what you did and why. It is easy to forget the reasoning behind your choices. A flow chart can help make it clear what the paths are through the program.