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Program
M
P
Objects
Are
@]
Defined in
Accessible in
Block:
Blocks
M
M, P, A, B, 0, R, S
P
P,A,B
A
A,B
Procedures
B
B
~
a
0, R,S
R
R
Is
I
S
S
Figure 9. Pascal Block Structure
Pascal defined in that document are described in the
following paragraphs.
Modifications. The precedence of Boolean
operators has been altered to that used in ALGOL
and FORTRAN. The CASE statement has an
OTHERWISE clause, and subrange case labels are
permitted. The WITH statement has a more reliable
form, although no upward compatibility from Pascal
has been lost. The FOR statement has a control
variable that is local to that statement. The use of
the GOTO statement has been restricted. PUT, GET,
and the file-buffer variable have been deleted from
the language; the standard functions READ and
WRITE have been generalized to nontext files.
Program parameters are no longer used for declaring
files. User-defined functions may not have side
effects.
Extensions. Data objects of type REAL can have
a minimum precision. Structured jumps out of
structured statements and procedures are allowed
using the ESCAPE statement. Both array and set
types can be "dynamic" in that their bounds can be
fixed during program execution. ASSERT statements
are included to aid program testing. Common
variables, which have global extent and scope as
dictated by ACCESS declarations, have been added
to the language. External procedures and functions
can be declared and communicated using a variety
of linkages. FIXED and DECIMAL standard types
have been added. Files can be declared as
RANDOM, and standard functions that operate on
random files are provided. The type structure can be
explicitly overridden using type transfer. Fuller type-
checking is included on procedure and function
parameters.
31
Sort/Merge
The DXlO operating system supports an optional
Sortl Merge package that can be accessed in several
ways. The SCI provides commands to access
Sortl Merge in batch or interactive mode. COBOL,
FORTRAN, and BASIC programs can interface with
Sortl Merge by using the CALL statement. Both sort
and merge support record selection, reformatting on
input, and summarizing on output.
Ascending key order, descending key order, or an
aiternate coiiating sequence can be specified. Any
number of keys can be specified as long as their
total length is less than 256 characters. The merge
process supports up to five input files. The sort
process allows full, address, key, and summary sorts.
Program-Development Tools
In addition to a comprehensive set of utilities that
operate in conjunction with the DXIO operating
system, Texas Instruments provides four major
program-development tools: interactive text editor,
macro assembler, link editor, and debug package.
Interactive Text Editor
The DXIO operating system provides an interactive
text editor that operates from either a record-
oriented interactive device or from one of the VDTs.
Edit operations are initiated by edit keys or by
command. When operations are initiated by
commands, parameters are necessary and are
prompted by the DX 10 system. Edit operations
allow modification, insertion, and deletion of entire
records or of character strings within records.
Macro Assembler
The DX 1 0 system assembler is the most powerful of
the 990 family assemblers. In addition to accepting
the standard 990 assembly-language instructions, the
macro assembler is extended to include a macro
facility, support for FORTRAN common segments,
and conditional assembly. The macro facility
provides character-string manipulation, accesses
binary values in the symbol table, and supports
macro-definition libraries. The relocatable object
code produced by the assembler can be partitioned
into segments. Common blocks, program segments,
and data segments are assigned separate location
counters. The link editor collects segments of the
same type in contiguous memory areas. A sequence
of assembly-language statements can be conditionally
processed depending on the value of the assembler
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