TELCOMP was a programming language developed at Bolt, Beranek and Newman (BBN) in about 1965 and in use until at least 1974.
It was an interactive, conversational language based on JOSS, developed by BBN after Cliff Shaw from RAND visited the labs in 1964 as part of the NIH survey. It was first implemented on the PDP-1 and was used to provide a commercial time sharing service by BBN in the Boston area and later by Time Sharing Ltd. in the United Kingdom.
In 1996, Leo Beranek said "We even developed a programming language called TELCOMP that to this day, some say was better than the programming language that the industry adopted, namely BASIC."
There were at least three versions: TELCOMP I, TELCOMP II, and TELCOMP III.
TELCOMP programs were normally input via a paper tape reader on a Teletype Model 33, which would be connected to a PDP via a modem and acoustic telephone line. Data could be read from the paper tape reader or from the Teletype keyboard. Output was either printed to the Teletype or sent to the paper tape punch. Early versions had no facility for on-line storage of programs or data.
During data input using a Teletype, the user would type a response to a printed prompt. If, instead of hitting Return, the user hit Tab, another, possibly computed, prompt would be printed on the same line. This process could be repeated for the full width of the line. This unusual feature allowed very compact data entry, comparable to full-screen CRT data entry. It saved paper, and the input section of the form became part of the program's printed output.
A later derivative of TELCOMP called STRINGCOMP was oriented towards string handling. Another BBN JOSS-derivative called FILECOMP was developed for the GE MEDINET system, which was cancelled. The implicit file handling system it contained was influential on the MUMPS global database system.
A TELCOMP program was made up of numbered lines, each line referred to as a Step. Steps were grouped into Parts. Each line contained one instruction.
DEMAND Read input from the teletype DO PART Execute all of the steps in a numbered part DO STEP Execute a single line DONE Stop execution of current part and return to caller IF Condition, suffixed to any instruction FOR Loop, suffixed to any instruction PLOT Type output to the teletype in the form of a graph PRINT Print output to the teletype READ Read input from the paper tape reader SEND Send output to the paper tape punch SET Assign a variable to the value of an expression STOP Stop execution completely TO PART Go to a specified part TO STEP Go to a specified line TYPE Emulate teletype input while in stored operation mode (like the TCL/TK Expect functionality) ; Comment, suffixed to any line FORM A specification for formatted output (not really a command)
Sample Program 
1.04 TYPE #,"ENTER ONE OF THE FOLLOWING:-";MENU 1.05 TYPE FORM X FOR X=1:1:4 FOR END=10^15 1.06 READ GRNO IN FORM 15 1.065 DONE IF GRNO=END 1.07 TO STEP 1.06 IF GRNO>4 1.08 TO PART GRNO+1 2.01 DO PART 50 2.02 READ N,K 2.03 DO PART 51 2.04 TO PART 15 .. 15.01 LINE FOR X=1:1:3 15.02 TYPE MINPL,MAXPL IN FORM 17 15.03 TYPE FORM 17 15.04 DO PART GRNO+15 FOR X=MNPL:STPL:MXPL 16.01 Y=(X^N)+K 16.02 Y1[X]=(((Y-MNPL)/(MXPL-MNPL))*2)-1 .. FORM 15 ITEM NUMBER? ##### FORM 17 MINIMUM ##### MAXIMUM ######