In this section, we will cover the fundamental syntax and structure of MUMPS (M) programming. Understanding these basics is crucial for writing and reading MUMPS code effectively.

1. Lines and Commands: MUMPS code is written in lines, each containing one or more commands.
2. Labels: Lines can be labeled for reference, which is useful for branching and subroutines.
3. Variables: Variables in MUMPS can be local or global, and they do not require explicit declaration.
4. Comments: Comments are used to annotate code and are ignored by the interpreter.

Each line in MUMPS can contain one or more commands. Commands are separated by spaces, and each command can have arguments.

• WRITE is a command that outputs text to the screen.
• "Hello, World!" is the argument to the WRITE command.
• ! is a special character that moves the cursor to the next line.

Labels are used to mark lines of code for reference. They are placed at the beginning of a line and followed by a space.

• START and END are labels.
• GOTO END transfers control to the line labeled END.
• QUIT terminates the execution of the current routine.

Variables in MUMPS can be local or global. Local variables are only accessible within the current routine, while global variables are accessible across different routines and sessions.

• SET X=10 assigns the value 10 to the local variable X.
• WRITE "The value of X is: ", X,! outputs the value of X.

Global variables are prefixed with a caret (^).

• SET ^GLOBALX=20 assigns the value 20 to the global variable ^GLOBALX.
• WRITE "The value of ^GLOBALX is: ", ^GLOBALX,! outputs the value of ^GLOBALX.

Comments in MUMPS are denoted by a semicolon (;). Everything after the semicolon on a line is ignored by the interpreter.

• ; This is a comment is a comment and will not be executed.
• The second WRITE command is commented out and will not be executed.

Let's put these concepts together in a simple program:

1. Labels: START is the label marking the beginning of the program.
2. Comments: Comments are used to explain each section of the code.
3. Variables: X, Y, and Z are local variables.
4. Commands: SET is used to assign values, and WRITE is used to output text.

Write a MUMPS program that calculates the product of two numbers and displays the result.

Solution:

Modify the above program to use global variables instead of local variables.

Solution:

• Forgetting to use spaces: Ensure there is a space after labels and between commands.
• Incorrect variable usage: Remember to differentiate between local and global variables.
• Missing QUIT: Always end your routines with QUIT to avoid unexpected behavior.

In this section, we covered the basic syntax and structure of MUMPS programming, including lines and commands, labels, variables, and comments. Understanding these fundamentals is essential for writing and reading MUMPS code. In the next module, we will delve into basic programming concepts such as variables, data types, and control structures.