GwBasic Compiler / Interpreter

DESCRIPTION BY WIKIPEDIA
GW-BASIC is a dialect of the BASIC programming language developed by Microsoft from BASICA, originally for Compaq. It does not need the ROM BASIC. The language is suitable for simple games, business programs and the like. it is also a low-cost way for many aspiring programmers to learn the fundamentals of computer programming.
GW-BASIC has a command line-based integrated development environment (IDE) based on Dartmouth BASIC. Using the cursor movement keys, any line displayed on screen can be edited. It also includes function key shortcuts at the bottom of the screen. Like other early microcomputer versions of BASIC, GW-BASIC lacked many of the structures needed for structured programming such as local variables, and GW-BASIC programs executed relatively slowly, because it was an interpreted programming language. All program lines must be numbered; all non-numbered lines are considered to be commands in direct mode to be executed immediately. Program source files are normally saved in binary compressed format with tokens replacing commands, with an option to save in ASCII text form.
The GW-BASIC command-line environment has commands to RUN, LOAD, SAVE, LIST the current program, these commands can also be used as program statements. There is little support for structured programming in GW-BASIC. All IF/THEN/ELSE conditional statements must be written on one line, although WHILE/WEND statements may group multiple lines. Functions can only be defined using the single line DEF FNf(x)= statement (e.g., DEF FNLOG(base,number)=LOG(number)/LOG(base)). The data type of variables can be specified with a character at the end of the variable name: A$ is a string of characters, A% is an integer, etc. Groups of variables can also be set to default types based on the initial letter of their name by use of the DEFINT, DEFSTR, etc., statements. The default type for undeclared variables not identified by such typing statements, is single-precision floating point (32-bit MBF).