The macroinstructions that manipulate application program control blocks are:

• GENCB
• MODCB
• SHOWCB
• TESTCB

The advantages of these macroinstructions are that they:

• Provide in one instruction what would require several assembler language instructions
• Allow symbolic references to be made to control blocks and their fields without having to be concerned with their relative storage locations
• Can create control blocks in storage obtained dynamically, thereby allowing the application program to be reentrant.

The disadvantages of these macroinstructions are that they:

• Do not support newer parameters
• Are not efficient and expend CPU cycles.

For details about syntax and return codes for manipulative macroinstructions, refer to:

• Return codes for manipulative macroinstructions
• Summary of operand specifications
• Forms of the manipulative macroinstruction.