Programmable calculator including alphanumeric error display 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 oriented towards the environment of the user, a central processing unit, an input-output control unit for bidirectionally transferring information between the memory or central processing units and a number of input and output units. The memory, central processor, 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 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 output printer unit capable of printing on thermal sensitive paper every alphabetic and numeric character and many other symbols individually and in alphameric statements or messages. Syntactical errors in a line of one or more alphameric statements being entered into the calculator from the keyboard input unit are automatically detected and immediately indicated to the user as they occur. Nonsyntactical errors in a line of one or more alphameric statements previously entered into the calculator and stored as a program in the read-write memory are automatically detected during execution of the line in which the error is present. Such errors, together with identification of the erroneous line, are visually indicated to the user. Both syntactical and nonsyntactical errors are communicated to the user by way of visually displayed alphameric messages that indicate the nature of the error encountered. A number of editing keys are provided to permit the user to view the line of alphameric statements in which an error has been detected to facilitate efficient correction of that error.