MAP is a formatted layout that is divided into 24 rows where each row is divided into 80 columns. MAP fits to the terminal screen display to send and retrieve the data.
Each column is accessible by the system to display the data to the user or retrieve the information entered by the user. MAP layout is designed by the assembler macros called Basic Mapping Support (BMS) macros.
Basic mapping support (BMS) is an application programming interface between CICS programs and terminal devices. MAPs are grouped as MAPSET based on its characteristics and usage. Each MAP has divided into fields for the retrieval or displaying data. MAP hierarchy is specified below -
Once the MAP format designed with BMS macros, it needs the MAP structure to compile the MAP to get loaded into display. The MAP divided into two types based on the its creation and usage.
- Physical MAP
- Symbolic MAP
Physical MAP -
Physical map is the load module produced after link-edit process of the MAP which is created by using BMS macros. Physical map controls screen alignment of MAP and represents the display format of the terminal.
Physical maps used to display data to the terminal and as well as receive the data from terminal. Physical map assembled and link edited into CICS LOAD LIBRARY after the successful compilation.
Physical map ensures the device independence in application programs. Physical map contains the details of unnamed fields and named fields attribute, position and length details. Physical map is stored in the same load library where the application program loads are stored.
Symbolic MAP -
Symbolic Map is the structure of the MAP represents as a copy library member. Symbolic map is used in application program to define and access the fields of the MAP.
Symbolic map can be used to define the map fields for storing the data in the application program. Symbolic Map can be coded manually by the application developer.
After assembling, symbolic MAPs are stored in copy library. When symbolic maps are used in the program with COPY, those will copy into CICS region.
Symbolic Map mainly ensures the device and format independence to the application programs. Symbolic Map consists of all the named fields and five sub fields are created for each named field has. Each symbolic map named field has divided into the below five sub fields -
- Length Field
- Flag Field
- Attribute Field
- Input Field
- Output Field
The sub fields are called as symbolic variables and we will discuss in detail about them in further chapters.