INTX is an interactive programing and debugging system operating under UCLA's URSA interactive console system. Although originally designed as a debugging aid for interactive processor development, the addition of an on-line Assembler makes it a programing system in its own right. INTX operates only on the Computer Communications 301 graphics display device making use of automatic update and cursor positioning facilities. There are three major divisions in the system: (1) Command analysis and initialization, (2) Assembler-loader and (3) Interpreter - disassembler. The Command module displays an initial screen describing functions available, current level of development, and supervises the operation of all other components of the system. The Assembler is a subset of Basic Assembler Language with extended branch mnemonics which accepts standard assembly language and the EQU pseudo operation. The Interpretor module is designed to execute any System/360 instruction except the SVC. Any instruction that could be successfully executed by a program running in problem state is supported. [Related documents are LI 003610, LI 003611, LI 003645, LI 003646 and LI 003648.] (Author/SJ)