Glossary

A51

The standard 8051 Macro Assembler.

AX51

The extended 8051 Macro Assembler.

A251

The 251 Macro Assembler.

ANSI

American National Standards Institute. The organization responsible for defining the C language standard.

argument

The value that is passed to a macro or function.

arithmetic types

Data types that are integral, floating-point, or enumerations.

array

A set of elements, all of the same data type.

ASCII

American Standard Code for Information Interchange. This is a set of 256 codes used by computers to represent digits, characters, punctuation, and other special symbols. The first 128 characters are standardized. The remaining 128 are defined by the implementation.

batch file

An ASCII text file containing commands and programs that can be invoked from the command line.

Binary-Coded Decimal (BCD)

A BCD (Binary-Coded Decimal) is a system used to encode decimal numbers in binary form. Each decimal digit of a number is encoded as a binary value 4 bits long. A byte can hold 2 BCD digits – one in the upper 4 bits (or nibble) and one in the lower 4 bits (or nibble).

BL51

The standard 8051 linker/locator.

block

A sequence of C statements, including definitions and declarations, enclosed within braces ({ }).

C51

The Optimizing C Compiler for classic 8051 and extended 8051 devices.

CX51

The Optimizing C Compiler for Philips 80C51MX architecture.

C251

The Optimizing C Compiler for Intel/Atmel WM 251.

constant expression

Any expression that evaluates to a constant non-variable value. Constants may include character and integer constant values.

control

Command line control switch to the compiler, assembler or linker.

declaration

A C construct that associates the attributes of a variable, type, or function with a name.

definition

A C construct that specifies the name, formal parameters, body, and return type of a function or that initializes and allocates storage for a variable.

directive

Instruction or control switch to the compiler, assembler or linker.

escape sequence

A backslash (‘\’) character followed by a single letter or a combination of digits that specifies a particular character value in strings and character constants.

expression

A combination of any number of operators and operands that produces a constant value.

formal parameters

The variables that receive the value of arguments passed to a function.

function

A combination of declarations and statements that can be called by name to perform an operation and/or return a value.

function body

A block containing the declarations and statements that make up a function.

function call

An expression that invokes and possibly passes arguments to a function.

function declaration

A declaration providing the name and return type of a function that is explicitly defined elsewhere in the program.

function definition

A definition providing the name, formal parameters, return type, declarations, and statements describing what a function does.

function prototype

A function declaration that includes a list of formal parameters in parentheses following the function name.

in-circuit emulator (ICE)

A hardware device that aids in debugging embedded software by providing hardware-level single-stepping, tracing, and break-pointing. Some ICEs provide a trace buffer that stores the most recent CPU events.

include file

A text file that is incorporated into a source file.

keyword

A reserved word with a predefined meaning for the compiler or assembler.

L51

The old version of the 8051 linker/locator. L51 is replaced with the BL51 linker/locater.

LX51

The extended 8051 linker/locator.

L251

The 251 linker/locator.

LIB51, LIBX51, LIB251

The commands to manipulate library files using the Library Manager.

library

A file that stores a number of possibly related object modules. The linker can extract modules from the library to use in building a target object file.

LSB

Least significant bit or byte.

macro

An identifier that represents a series of keystrokes.

manifest constant

A macro that is defined to have a constant value.

MCS® 51

The general name applied to the Intel family of 8051 compatible microprocessors.

MCS® 251

The general name applied to the Intel family of 251 compatible microprocessors.

memory model

Any of the models that specifies which memory areas are used for function arguments and local variables.

mnemonic

An ASCII string that represents a machine language opcode in an assembly language instruction.

MON51

An 8051 program that can be loaded into your target CPU to aid in debugging and rapid product development through rapid software downloading.

MON251

A 251 program that can be loaded into your target CPU to aid in debugging and rapid product development through rapid software downloading.

MSB

Most significant bit or byte.

newline character

A character used to mark the end of a line in a text file or the escape sequence (‘\n’) to represent the newline character.

null character

ASCII character with the value 0 represented as the escape sequence (‘\0’).

null pointer

A pointer that references nothing. A null pointer has the integer value 0.

object

An area of memory that can be examined. Usually used when referring to the memory area associated with a variable or function.

object file

A file, created by the compiler, that contains the program segment information and relocatable machine code.

OH51, OHX51, OH251

The commands to convert absolute object files into Intel HEX file format.

opcode

Also referred to as operation code. An opcode is the first byte of a machine code instruction and is usually represented as a 2–digit hexadecimal number. The opcode indicates the type of machine language instruction and the type of operation to perform.

operand

A variable or constant that is used in an expression.

operator

A symbol (e.g., +, -, *, /) that specifies how to manipulate the operands of an expression.

parameter

The value that is passed to a macro or function.

PL/M-51

A high-level programming language introduced by Intel at the beginning of the 1980’s.

pointer

A variable containing the address of another variable, function, or memory area.

pragma

A statement that passes an instruction to the compiler at compile time.

preprocessor

The compiler’s first pass text processor that manipulates the contents of a C file. The preprocessor defines and expands macros, reads include files, and passes control directives to the compiler.

relocatable

Object code that can be relocated and is not at a fixed address.

RTX51 Full

An 8051 Real-time Executive that provides a multitasking operating system kernel and library of routines for its use.

RTX51 Tiny

A limited version of RTX51.

RTX251 Full

An 251 Real-Time Executive that provides a multitasking operating system kernel and library of routines for its use.

scalar types

In C, integer, enumerated, floating-point, and pointer types.

scope

Sections of a program where an item (function or variable) can be referenced by name. The scope of an item may be limited to file, function, or block.

Special Function Register (SFR)

An SFR or Special Function Register is a register in the 8051 internal data memory space that is used to read an write to the hardware components of the 8051. This includes the serial port, timers, counters, I/O ports, and other hardware control registers.

source file

A text file containing C program or assembly program code.

stack

An area of memory, indirectly accessed by a stack pointer, that shrinks and expands dynamically as items are pushed onto and popped off of the stack. Items in the stack are removed on a LIFO (last-in first-out) basis.

static

A storage class that, when used with a variable declaration in a function, causes variables to retain their value after exiting the block or function in which they are declared.

stream functions

Routines in the library that read and write characters using the input and output streams.

string

An array of characters that is terminated with a null character (‘\0’).

string literal

A string of characters enclosed within double quotes (“ ”).

structure

A set of elements of possibly different types grouped together under one name.

structure member

One element of a structure.

token

A fundamental symbol that represents a name or entity in a programming language.

two’s complement

A binary notation that is used to represent both positive and negative numbers. Negative values are created by complementing all bits of a positive value and adding 1.

type

A description of the range of values associated with a variable. For example, an int type can have any value within its specified range (-32768 to 32767).

type cast

An operation in which an operand of one type is converted to another type by specifying the desired type, enclosed within parentheses, immediately preceding the operand.

Vision2

An integrated software development platform that supports the Keil Software development tools. Vision2 combines Project Management, Source Code Editing, and Program Debugging in one environment.

whitespace character

Characters used as delimiters in C programs such as space, tab, and newline.

wild card

One of the characters (? or *) that can be used in place of characters in a filename.