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Variables

What are Variables?

• Data are usually stored in computer memory.

• Variables are identifiers for your data. A variable act as a label to a memory location where the data is stored.

• Variable names are NOT stored inside the computer memory, and the compiler replaces them with memory location addresses during data manipulation.

Rules for Naming a Variable

• Make sure that the variable name is not longer than 30 characters. Some compilers may issue errors if the name is too long.

• A variable name can only contain:

  • Alphabets (upper/loser case)

  • Digits

  • Underscore

  The first letter of the variable CANNOT begin with a digit. (Only underscore or alphabet is allowed.)

• Cannot use C standard reserved keywords as variable names.

Defining Variables

• A variable can be used only after it is defined.

• A variable definition instructs the compiler to set a side memory space for the variable.

Variable Definition vs. Declaration

• A variable is defined when the compiler generates instrctuions to allocate the storage for the variable.

• A variable is declared when the compiler is informed that a variable exists along with its type. The compiler does not generate instructions to allocate the storage for the variable at that point.

• A variable definition is also a declaration, but not all variable declarations are definitions.

References

Nayak, K. (2022). Microcontroller Embedded C Programming: Absolute Beginners [Video file]. Retrieved from https://www.udemy.com/course/microcontroller-embedded-c-programming/