APAL - A Processor Assembler Language


INTRODUCTION

An APAL program is composed of one or more APAL source statements.
Each statement is one line in length. Each statement, when com-
piled by the APAL compiler, results in one or more instructions to
be executed by the A processor, or the definition of working memory
space for the program. The APAL compiler examines each source state-
ment for proper syntax and usage of operands. Any errors are noted
on the compile listing which is a product of the compilation process.
The compiler generates instructions, assigns memory addresses, and
sets aside memory areas for buffers and working space as directed by
the source statements in the program.

The console command to execute the APAL compiler is: APAL A B C.
A is the name of the file containing the source program. B is the
name of the file that will contain the binary at the completion of
the compilation process. C is the name of the file that will contain
the listing.


STATEMENT FORMAT

The basic APAL instruction takes the form of a conditional assignment
statement.


Label Assignment Expression , Condition Expression .Comments


 #
 Subject1 = Expression1, Subject2 = Expression
 <
 >

Except for a very limited number of statements, all APAL source
statements take this form. The assignment portion of the statement
is always present, and is composed of a single subject followed by an
= sign followed by an expression which expresses the value of the
quantity which is to replace the subject operand. The = sign is the
only separator allowed between the subject and the replacement ex-
pression in the assignment portion of the statement. Expression1 may
be any expression composed of valid names ond operators. The condition
portion of the statement is optional. When present, it is first eval-
uated to determine a true or false condition. If true, the assignment
portion of the statement is executed. If false, the assignment portion
of the statement is not executed. If 

[file broken from here]