Introduction
This chapter will provide the background necessary to begin using the THEOS operating system. We will begin by defining what a documentation convention is. Next, THEOS system conventions such as how disks are "searched," how to assign names to files, using wildcards, and system control keys will be discussed. We will conclude by defining the concept of a command line and giving a few examples of how to enter THEOS commands.
In this chapter a number of screen displays will be included in the discussion. In these displays, items to be entered via the keyboard by the reader are shown in boldface. <RETURN> will indicate that the Return key is to be pressed.
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46 THEOS User's Handbook
If you have access to a computer with THEOS software, study this chapter while seated at a terminal. Enter the examples and compare the screen displays on your terminal with the illustrations provided.
THEOS Documentation
In order to use THEOS certain rules or instructions must be followed when typing commands for the computer system to interpret.
The rules governing the correct way to type a THEOS command are called documentation conventions. It is important to follow these documentation conventions because they provide a means of commun-icating with the operating system. Some examples of documentation conventions are:
• Abbreviations
• Delimiters and special characters such as asterisks (*), commas (,), equal signs (=), parentheses( ), periods (.), spaces ( ), and colons (:).
Abbreviations are the shortest form of a THEOS command.
Available THEOS command abbreviations will be indicated in the tutorial section on commands.
Delimiters and special characters in THEOS are used much like punctuation is used in languages to clarify thoughts and expressions.
The a&terisk (*) is called a wildcard character and will be discussed in the section of this chapter titled wildcards. The other special characters will be discussed as required.
THEOS System Conventions
THEOS system conventions are the set of rules that the operating system uses to perform tasks such as finding files, erasing files, storing files, determining when each user can access the printer, etc. Every time THEOS is directed to perform a task, these rules are strictly followed.
The conventions cannot be changed but as you will see, they can be used to improve the speed and efficiency of computer operations.
STANDARD SEARCH ORDER
Standard search order is the order in which all disk drives on the computer system are searched when a disk operation is performed.
Since the access time required to locate files on disk is affected by their location, this makes standard search order an important convention.
When searching for data files and programs, disks are searched in alphabetical order: A,B,C,D,E,F,G,S. If you want to maximize access time, program files and data files should be located on the disks that will be searched first!
The disk labelled S is a special disk in that it is designated as the system disk. The system disk can be either a floppy disk or a hard disk.
It is used to boot or start the system and contains all of the operating system commands. It may contain other files as well depending ~pon
its storage capacity.
EXCEPTIONS TO STANDARD SEARCH ORDER
One exception to the standard search order is operating system commands or special programs called execs. The standard search order for commands or execs is disk S followed by disks A through G.
Another exception occurs when a command is executed, a data file is written, and no disk drive is specified. In such an instance the system disk is examined for blank space. If insufficient room is avail-able there, the other disks will be searched in alphabetical order until sufficient space is found to write the file.
PROMPTING CHARACTERS
Prompting characters are printed on the screen when the compu-ter is waiting for an entry. This book will only be concerned with the following THEOS prompts:
> The command string interpreter is waiting for a command.
* TEXTEDIT or EDIT is waiting for a command.
An EXEC is waiting for an entry.
t
A full screen of data has been displayed and the sys-tem is ready to disply the next data screen. Press<RETURN>.,
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The> is the primary THEOS prompting character and is the one most frequently encountered by users. Examples of entries to be made in response to these other prompting characters will be given later.
FILENAME, FILETYPE, FILEDISK
A filename is a unique name that identifies a program or data file.
A filename can consist of from one to eight characters. The first character must be a letter. A filename can only contain letters, digits, or a dollar sign.
Filetype is used to further describe the filename and indicates its function. A filetype of DATA could indicate a data file, while a filetype of COMMAND implies a THEOS command file. A filetype can consist of from one to eight characters. The first character must be a letter and like the filename, only letters, digits, or dollar signs are allowed for the remaining characters.
Filedisk is a letter assigned to a particular drive S, or any letter A through G. Generally, one need not specify a filedisk unless a file is to be written to a specific disk or file access time is to be reduced. If a filedisk is not specified, the system will search all available disks according to the rules of standard search order.
Filename, filetype, filedisk always appear in this order separated by a space ( ) or by a period (.). Filedisk can be omitted. In such instances, the proper order is filename.filetype. The combination of filename, filetype, and filedisk together are referred to as a file descrip-tion. Uppercase letters are always used to indicate file descriptions.
Whenever the THEOS prompt is on the screen, any letters typed automatically appear in upper case.
*
It is not necessary to use the shift key.* THEOS versions 6.0 and above now support either upper or lower case file descriptions.
Table 3.1. Examples of THEOS file descriptions SAMPLE.DATA S
ASSIST.EXEC G
TERMINAL.COMMAND S AROIAO.DF C
LETTER1.WPF D LETTER1.BACKUP B ACCTING DATA A ACCTING BACKUP
Note that either a period or a space can be used to separate the filename, filetype, and filedisk.
THEOS Reserved File Descriptions
THEOS has a number of reserved file descriptions. When a file description is reserved for THEOS, this means that it cannot be used to name a data or program file. Table 3.2 indicates the file descriptions reserved for THEOS.
Table 3.2. THEOS Reserved File Descriptions IPL.EXEC
SYSTEM.NUCLEUS SYSTEM.CSI SYSTEM. EXEC SYSTEM.DEVNAMES SYSTEM.ACCOUNT SYSTEM.HISTORY SYSTEM.ERRMSG SYSTEM.EXEC SYSTEM.SPOOLER SYSTEM.SPOOLQUE SYSTEM.DEVn SYSTEM.CLASSn HELP.COMMAND
In addition there are certain filetypes reserved for use by THEOS.
File descriptions with these filetypes may not be used to name data or program files.
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Table 3.3. THEOS Reserved Filetypes ASSEMBLE
WILDCARDS AND OTHER SPECIAL CHARACTERS
There are a number of characters which have special meaning to THEOS. These special characters are called wildcards.
They are:
* ? @ # =
Because of their special use you should not use these characters in file descriptions. In fact, avoid the use of any symbols on the keyboard when naming files.
In most of the examples provided we indicate files using a specific file description. You may also use wildcards to specify a file or a group of files to eliminate keystrokes. Consider the following wildcard characters:
* ? @ # =
When THEOS encounters these characters as part of a filename, it replaces the filename with a sorted list of matching filenames from the disk directory.
WHAT THE WILDCARD CHARACTERS DO
• The * matches any string of alphanumeric characters in the file description.
• The? indicates that a single character in this position will match.
• The @ indicates that a single alphabetic character in this position will match.
• The # indicates that a single numeric character in this position will match.
• The = is used only in the COPYFILE and RENAME THEOS commands and will be discussed in those sections.
The use of wildcards and special characters is best illustrated with examples.
Type the following entries shown in boldface.
>FILELIST ATTACH.COMMAND <RETURN>
The system will display information about the file ATTACH.-COMMAND on the screen.
>FILELIST A*.COMMAND <RETURN>'
The system will display a list of all filenames that begin with the letter A and have a filetype of COMMAND.
Wildcard characters can be used in combination with each other.
Consider the following examples:
>TEST*.F??????# S
This file description indicates that all files whose filename starts with the letters TEST, whose filetype starts with the letter F, has a number in the eighth position, and is on the S drive are to be included.
>@@@@??#*.?? *
This file description indicates that all files should be included whose name is at least seven characters long, of which the first four characters are alphabetic (four@'s), the next two may be any character
52 THEOS User's Handbook
(n), the seventh character is numeric (#) and the eighth character may be anything including a space (*). The filetype must be two alphanu-meric characters (n) and may be located on any disk (*).
To summarize, wildcard characters are a useful addition to THEOS because it is not always possible to remember an exact file description. Wildcards can be used in place of an exact file description.
They provide users with a method of finding files when a memory lapse occurs, and help eliminate the burden of memorizing numerous file descriptions.
SYSTEM CONTROL KEYS
System control keys are special key sequences which perform specific functions under THEOS. There are a total of 12 key sequences that are a part ofTHEOS but for now we will only deal with the system cancel key. The key sequence ESC Q (this means hit the ESCape key and then press Q) is called the system cancel key. Its function is to terminate the execution of any system operation in progress, thereby returning the user to the operating system prompt>.
Caution: try not to get into the habit of using ESC Q. It should only be used when an operation can be cancelled without the risk of losing data.
THE THEOS COMMAND LINE
In the next chapter, we will present a series of tutorials designed to teach you to use the operating system. Throughout the tutorials we will consistently use the symbols and procedures outlined below:
• The ">" indicates the THEOS operating system prompt.
THEOS automatically prints this character on an oth-erwise empty line to tell you it is ready to accept your next entry.
• A THEOS system command is a program which per-forms some desired function. For example, SHOW DISK is a command that displays information aboutthe disk drives in a THEOS system. THEOS commands are shown in uppercase boldface type.
• A command line includes all the characters typed fol-lowing the THEOS prompt until you press the return key to indicate you wish to terminate the entry.
• A command line consists of one or more distinct ele-ments. Each element is a sequence of alphanumeric characters separated from other elements by either a space ( ) or a period (.).
• The first element immediately after the> prompt is always the name of the command. For simple com-mands (such as HELP) you type the command and then terminate the command line by pressing the return key.
• For more complex commands, you type the command name, a space or a period, followed by one or more elements, which specify additional information.
• Command operands are keyword and variable symbols of not more than eight alphanumeric characters. These keywords and variables specify the information on which THEOS operates when it performs the command function. Examples of command operands are file-name, filetype, and filedisk. Some commands require no operands while others require several.
• Command options are keywords used to control execu-tion of the command. The most frequently used com-mand options will be listed with each comcom-mand in the next chapter. The first option must be preceded by a left parenthesis - a closing parenthesis is not required.
Each THEOS command may have a number of options associated with it.
• Default options are certain command options that are performed automatically unless otherwise specified.
When default options are LJsed, it is not necessary to use a left parenthesis unless you wish to include some non-default options.
• All input to the keyboard, when typing command lines, is automatically "folded" into upper case. It is not necessary to use the shift key.
How To Enter Command Lines
Command lines are always entered in the following format:
command name operands (options ...
Consider the following THEOS command line:
>COPYFILE FILENAME.FILETYPE S = = G <RETURN>
54 THEOS User's Handbook
Here,
">"
is the THEOS prompt; "COPYFILE" is the command name; "FILENAME, FILETYPE, and S" are operands; the "=" signs are special characters which indicate that the same filename and file-type are to be used when the file is copied to disk drive G.Summary
In this chapter we have provided you with the necessary concepts to continue your study of THEOS. The best way to learn about THEOS is to use it. In the next chapter we will present a series of tutorials designed to teach you to use the operating system.