1. A data processing system having a program structure and execution mode where an actual argument is bound to a formal argument of a function to be called by storing a pair of a variable name as the formal argument and a variable as the actual argument into a First-In-Last-Out stack memory as an environment list, the function called executes processings using a latest bind value from said environment list when referring to variable values, when a value of such function is obtained, said function value is returned by deleting the formal argument variable of the function from said environment list, said system comprising: counter means for incrementing one and decrementing one for each call and return of the function, respectively; associative buffer memory means, operatively connected to said counter means, for storing words where each word comprises the variable name, location data for the variable name, location data for the variable on the environment list of said stack memory and a count value of said counter means when variables are stored in said stack memory; means for accessing said associative buffer memory means, responsive to a process reference to a variable for supplying the variable name as a key to said buffer memory means, for comparing said supplied variable name to the variable names stored in said buffer memory and for providing an indication of said comparison, responsive to an indication that said variable name is stored in said buffer memory means for obtaining a value for the variable name on the environment list using the location data corresponding to the variable name in the buffer memory means, responsive to an indication that said variable name is not stored in said buffer memory for obtaining a value for the variable name by searching variable names stored on said environment list and, responsive to a return from the function called for deleting the word of the buffer memory means which contains said counter value for said function.