Programmable calculator including program trace means

Abstract

An adaptable programmable calculator is provided by employing modular read-write and read-only memory units capable of being expanded to provide the calculator with additional program and data storage functions, a central processing unit, and an input-output control unit capable of bidirectionally transferring information between the memory or central processing units and a number of input and output units. The memory, central processing, and input-output control units are controlled by a microprocessor included in the central processing unit. The input and output units include a keyboard input unit, a magnetic card reading and recording unit, a solid state multi-character display unit capable of displaying every alphabetic and numeric character and many other symbols individually and in a line of one or more alphameric statements, and an alphameric printer unit. The calculator includes a TRACE key that permits the user to manually or programmably obtain an alphameric print-out of the number of each line of alphameric statements executed by the calculator and the value of each numeric assignment made therein. The calculator includes a NORMAL key for permitting the user to manually or programmably terminate a previously established TRACE mode of operation. An alphameric listing of each line of one or more alphameric statements, as that line is being executed by the calculator or stored as part of a program in the calculator read-write memory, may be obtained when the calculator is operating in the TRACE mode.