The text read off it
[page 38]
Presentation of Commands and Examples
In the following description of the specific elements of the Commercial Translator procedure vocabulary, each command is represented in its "general form." In each case the general form is enclosed in a rectangular frame to distinguish it from text and examples. The verbs and other words which are a fixed part of the language appear in the general forms in boldface capital letters. The words and phrases representing names, clauses and sentences which will be written by the programmer are shown in lower-case italics. For reference purposes, the same general forms are presented in Appendix 2 in a more concise manner, without any discussion. For those commands that may contain a variable number of operands, a construction such as, "data.name.1, data.name.2, . . . data.name.n" is used to indicate that as many as "n" operands may be specified by the programmer. It is important to note that, except for imbedded periods within italicized words, any punctuation shown in the general form of a command is a fixed and necessary part of the command.
In contrast to the general forms, examples of the various commands are written completely in capital letters and are not enclosed in frames.
Program Commands
Each of the Commercial Translator program commands causes some event or series of events to take place at object time, that is, the time at which the object program is run. The program commands are discussed, in turn, in the following pages according to the classification shown on the first page of this chapter.
Input/Output Commands
Within the category of program commands it is helpful to consider the input/output commands as a subgroup. The control of data flow through the data processing system is accomplished by means of an input/output control system. This system is called into play when the programmer uses one of the input/output commands in a statement of the procedure to be executed. The four verbs associated with these commands are OPEN, GET, FILE, and CLOSE.
Using the input/output commands, the programmer initiates the movement of data into buffers or internal storage, the checking of the validity of the file itself, the checking of the validity of the input or output operation, the storage of data in internal storage to insure its availability when required, and finally, the making available or filing away of data according to the needs of the program. Thus the input/output control system provides data flow control and, where feasible, a "look ahead" at the data flow.
The input/output control system in the Commercial Translator is a record processing system. That is, the unit of data which is made available by the system and on which attention is focused during each processing cycle is the record. Should the needs of the program require that more than one record from a file be made available for processing at one time, it will be necessary for the programmer to provide working storage into which he will move the additional records as required.
The input/output control system provided in the initial version of the Commercial Translator is intended for the handling of tape and card files. The detection of errors is an implicit part of the tape and card handling system; error correction, where feasible, is handled automatically. More specific information on the use of the data flow control vocabulary is presented in the following paragraphs.