Like RPG II, display formats are built from column-sensitive specifications which describe fields of fixed sizes with fixed or conditioned properties.
The System/36 version of SDA gained the H specification, which describes the displays used when the operator presses the "Help" key. The "Help" key can summon one display, a series of displays, or open an online document created by DisplayWrite/36 and position it to a certain page using a "bookmark." If "Help" is program-coded, program control resumes when "Help" is pressed; in this instance, the program determines what action to take. If "Help" was not coded at all, a keyboard error occurs, stating that the Help key is not allowed now.
All display formats have exactly one coded S specification, which describes the size of the format, the keys which may be used, the lines to be cleared, special functions such as sounding the Alarm (the "raspberry" sound is the only sound a S/3X terminal can be programmed to make), and most importantly the name of the format which must be referenced by the HLL (High-Level Language) program.
Display formats may have one, many, or no D ("Detail") specifications to describe the field(s) used in the display. These fields may be constants, input, output, or input-output. Properties such as Nondisplay and Protected may seem to defeat the purpose of having the field, but there are non-intuitive uses for these fields. D specifications must state the starting line and column number used by the field; whether attributes or color are used; and, if a constant is declared, the value can also be declared. An "X" is used for continuation D specification(s) when a constant is larger than 24 characters. In order to accommodate displays created with the larger 27x132 capabilities, an odd system of hexadecimal entries is allowed for the column position.
Display formats are so attuned to the RPG II language as to require language extensions when used with other HLLs. The 99 numbered RPG indicators perfectly match the screen indicators; however, when coding display formats, it is important to reserve indicator usage to match the current conditioning of the indicator when the display is written - otherwise, a dummy indicator used for Half-Adjust may end up positioning the cursor incorrectly.
Coding for the audience
When the IBM System/34 was sold, a common monitor would be a monochrome 12-inch IBM 5251; in the System/36 heyday, a common monitor would be the 12-inch IBM 5291 or the color 14-inch IBM 3486. Later in the S/36 life, third parties began to rise in popularity with such names as IIS, Decision Data, and Emerald. Not only do the third-party monitors cost much less, they offer multiple session capability, programmable color palettes, larger display areas, and a direct PC printer port which allows S/36 users to access inexpensive inkjet printers without a separate adapter. The "blue" or "red" field one codes may not appear blue or red on all audience equipment.
All S/34 and S/36 display stations use 5250 protocol; S/34 allows either 960-character displays or 1920-character displays; S/36 allows either 1920-character displays or (rare) 3564-character displays.
Two different display formats should be coded if it is possible that the audience might use the IBM 5252 Dual Display, which requires 960-character displays. Whether the audience will be using color or monochrome displays is a consideration - an application developed for color-only might not function well on a monochrome display.
Fortran is a general-purpose, compiled imperative programming language that is especially suited to numeric computation and scientific computing.
The IBM 3270 is a family of block oriented display and printer computer terminals introduced by IBM in 1971 and normally used to communicate with IBM mainframes. The 3270 was the successor to the IBM 2260 display terminal. Due to the text color on the original models, these terminals are informally known as green screen terminals. Unlike a character-oriented terminal, the 3270 minimizes the number of I/O interrupts required by transferring large blocks of data known as data streams, and uses a high speed proprietary communications interface, using coaxial cable.
A punched card is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to directly control automated machinery.
The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube logic and were made obsolete by the introduction of the transistorized 7000s. The 7000s, in turn, were eventually replaced with System/360, which was announced in 1964. However the 360/65, the first 360 powerful enough to replace 7000s, did not become available until November 1965. Early problems with OS/360 and the high cost of converting software kept many 7000s in service for years afterward.
Newline is a control character or sequence of control characters in character encoding specifications such as ASCII, EBCDIC, Unicode, etc. This character, or a sequence of characters, is used to signify the end of a line of text and the start of a new one.
A computer terminal is an electronic or electromechanical hardware device that can be used for entering data into, and transcribing data from, a computer or a computing system. The teletype was an example of an early-day hard-copy terminal and predated the use of a computer screen by decades.
RPG II is a very early and popular version of the IBM RPG programming language.
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The IBM System/32 introduced in January 1975 was a midrange computer with built-in display screen, disk drives, printer, and database report software. It was used primarily by small to midsize businesses for accounting applications. RPG II was the primary programming language for the machine.
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RPG is a high-level programming language for business applications, introduced in 1959 for the IBM 1401. It is most well known as the primary programming language of IBM's midrange computer product line, including the IBM i operating system. RPG has traditionally featured a number of distinctive concepts, such as the program cycle, and the column-oriented syntax. The most recent version is RPG IV, which includes a number of modernization features, including free-form syntax.
IBM 5250 is a family of block-oriented terminals originally introduced with the IBM System/34 midrange computer systems in 1977. It also connects to the later System/36, System/38, and IBM AS/400 systems, and to IBM Power Systems systems running IBM i.
The IBM System/3 is an IBM midrange computer introduced in 1969, and marketed until 1985. It was produced by IBM Rochester in Minnesota as a low-end business computer aimed at smaller organizations that still used IBM 1400 series computers or unit record equipment. The first member of what IBM refers to as their "midrange" line, it also introduced the RPG II programming language. It is the first ancestor in the product line whose current version is the IBM i series and includes the highly successful AS/400.
The text-only monochrome IBM 2260 cathode-ray tube (CRT) video display terminal plus keyboard was a 1964 predecessor to the more-powerful IBM 3270 terminal line which eventually was extended to support color text and graphics.
Operational Control Language (OCL) is the control language of the IBM System/32, System/34 and System/36 minicomputer family. It is supported on IBM i's System/36 Environment for backwards compatibility purposes. It is similar to the older control languages JCL (System/370) and System/3, and unrelated to the later Control Language, and REXX (AS/400).
RPG III is a dialect of the RPG programming language that was first announced with the IBM System/38 in 1978. An upgraded version, RPG IV, was introduced in 1994. In 2001 RPG was again updated to remove a number of column restrictions. RPG continues to be upgraded on a regular basis. The last fixed form restrictions were removed in 2015. Other than sharing some opcodes and terminology, modern RPG IV is visually very different from RPG III.
In computing, an attribute is a specification that defines a property of an object, element, or file. It may also refer to or set the specific value for a given instance of such. For clarity, attributes should more correctly be considered metadata. An attribute is frequently and generally a property of a property. However, in actual usage, the term attribute can and is often treated as equivalent to a property depending on the technology being discussed. An attribute of an object usually consists of a name and a value; of an element, a type or class name; of a file, a name and extension.
System Support Program (SSP) was the operating system of the IBM System/34 and System/36 minicomputers. SSP was a command-based operating system released in 1977.
IBM System/34 BASIC was an interpreter for the IBM System/34 midrange computer.
IBM System/36 BASIC was an interpreter for the IBM System/36 midrange computer.
