IBM 5280 Distributed Data System - Index of

The following illustration shows how the system table is used to find an edit formatcontrol string that is located within the partition. In the illustration, FMT02 isthe second edit format set up with a .FMT control statement series.Source: READ(3,FMT02,O,N)Object:12o,o3,oLiIBytes 24 and 25 ofthe Partition lOBSystem TableF F F FEdit Format Control String_I ISystem Table for Screen Format Control StringsThe system table for screen format control strings is built by the assembler when itprocesses the .SFMT control statements; one system table entry is generated fromeach series of .SFMT control statements. The address of the system table for screenformat control strings that are located within the partition is stored in the keyboard/display lOB at hex 79, relative to the start of the lOB. The address of the systemtable for global screen format control strings is stored in the system control block,with the storage page number at hex FB and the address at hex Fe.The system table for screen format control strings that are located within the partitionconsists of one 2-byte entry for each control string. The 2-byte entry containsthe address, relative to the beginning of the partition, where the control string islocated. There may be up to 256 control strings within a partition, represented bysystem table indexes 0 through 255.The system table for global screen format control strings consists of one 2-byteentry for each global control string. The 2-byte entry contains the address, relativeto the beginning of the storage page (in hex FB), where the control string is located.There may be up to 256 global control strings represented by system table indexeso through 255. The first global screen format control string is used by the systemfor the standard load prompt.The ENTR command in the source program includes the label of the screen controlformat to use. The assembler converts the label to the system table index, andalso determines whether the control string is within the partition or in the commonarea. If the control string is within the common area, bit 9 of the 4-byte objectcode instruction is set to 1. During program execution, if bit 9 equals 1 the addressof the system table is taken from the system control block. If bit 9 equals 0 theaddress of the system table is taken from the keyboard/display lOB within thepartition.Main Storage Data Areas 97