U UNIVAC 1218 - Bitsavers
U UNIVAC 1218 - Bitsavers
U UNIVAC 1218 - Bitsavers
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
10 BASIC INFORMATION<br />
SECTION III-A. TRIM I ASSEMBLY SYSTEM<br />
TRIM I is a simple assembly system which converts a source program tape written<br />
with symbolic addressing into an object program tape with absolute addressing<br />
suitable for loading into the computers via the utility packages.<br />
20 SYMBOLIC ADDRESSING<br />
201 LABELS<br />
In an absolute-addressed program every word is assigned an absolute address<br />
during the coding process. In the TRIM I system only those words which are<br />
referred to by instructions require an address, although the address is symbolic<br />
rBther than absolute. The term label is used rather than address since it more<br />
accurately describes the function of the symbolic address. A label may never<br />
be incremented or decremented. Words which are not referred to need not be<br />
labeled o<br />
Unlabeled words following one another on the source program tape are<br />
ultimately assigned to consecutive memory addresses. For any given assembly<br />
run each label used must be unique.<br />
Instructions are written with mnemonic or octal notation for the function and/<br />
or subfunction codes. The u or k portion of an instruction word may be either<br />
a constant, an octal notation,or a symbolic notation (alphanumeric) referring<br />
to a constant (either an absolute address or an item of data).<br />
Whenever any instruction refers to a label, the u portion of that instruction<br />
is called a tag. The tag must be identical with the label to which it refers<br />
but may be followed by a + or - and an octal integer to provide for increments<br />
or decrements. Thus an instruction may refer to an unlabeled instruction in<br />
terms of its sequential position preceding or following a labeled instruction.<br />
Symbolic addressing simplifies the task of coding. In addition it permits the<br />
transfer of programs to any region of memory since the symbolic addressed<br />
program is independent of memory locations.<br />
III-A-l