terminals until the advent of the screen editor in the late 1970s, and the programmer could single-step or check values of variables. Two rows of user-defined function keys with paper labels were some of the earliest implementation of general function keys. They would be the basis for later screen labeled function keys used in later Hewlett Packard (and IBM) terminals and computers, and now widely adopted in calculators, bank terminals, and gas pumps. It was programmable in BASIC, which could be extended with ROMs to do graphics plotting, matrix math and string variables. The ROM cartridges were designed to extend the BASIC language, and were very similar to the cartridges later used by video game consoles. The Plotter ROM added commands which made creating a chart much more simple than is possible with C++ or C#, and used either user or world coordinates rather than integer plotter units. These commands would later become the basis for the device-independent HP AGL graphics language standard implemented on other HP computers such as the HP 1000 minicomputer and HP 2647 intelligent graphics terminal. 10 REMARK DRAW A PARABOLA 20 SCALE -1.0, 1.0, -1.0, 1.0 30 FOR X = -1.0 TO 1.0 STEP 0.10 40 PLOT X, X*X 50 NEXT X 60 END Also available for programming the HP 9800 series was a bootable development environment based on UCSD Pascal. HPL Language description In HPL instead of variables such as A1 and J2, there were numbered registers r1, r2, up to r199999. The following HPL program for the HP 9825 generates a list of prime numbers: 0: fxd 0 1: prt 1 2: prt 2 3: 1→P 4: for C=2 to 1000000 5: P+2→P 6: for N=3 to P/3 7: if int(P/N)*N = P; gto 4 8: next N 9: prt P 10: next C Another unique characteristic of HPL was the right arrow. This arrow was known as the gazinta (slang for "goes into"). The statement 1→P would be pronounced "One gazinta P". Other BASIC computers The Data Terminals Division also produced a BASIC programmable version of the HP2640 series terminal, the HP 2647a, which also featured AGL, an HP standardization of the HP 9830 plotter commands. HP 2647 BASIC was essentially Microsoft BASIC with HP 9830-style plotting commands added, and was one of Microsoft's first big contracts with a mainstream computer company. HP also produced a series of handheld pocket computers with