The CDC 3000 series ("thirty-six hundred" of "thirty-one hundred") computers from Control Data Corporation were mid-1960s follow-ons to the CDC 1604 and CDC 924 systems. Over time, a range of machines were produced - divided into the 48-bit upper 3000 series and the 24-bit lower 3000 series. Early in the 1970s CDC phased out production of the 3000 series, which had been the cash cows of Control Data during the 1960s; sales of these machines funded the company while the 6000 series was designed. Specifications Upper 3000 series The upper 3000 series used a 48-bit word size. The first 3000 machine to be produced was the CDC 3600; first delivered in June 1963. First deliveries of the CDC 3400 and CDC 3800 were in December 1965. These machines were designed for scientific computing applications; they were the upgrade path for users of the CDC 1604 machines. However these machines were overshadowed by the upcoming 60-bit CDC 6000 series machines when the CDC 6600 was introduced in December 1964 and delivered in 1965. Some high-end computer labs purchased these machines as stopgaps, while waiting for delivery of their 6600 machine. (CDC had indicated that the 6600 machines would use the same assembler language.) Lower 3000 series The lower 3000 series used a 24-bit word size. They were based on the earlier CDC 924 - a 24-bit version of the (48-bit) CDC 1604. The first lower 3000 to be released was the CDC 3200 (May 1964), followed by the smaller CDC 3100 (February 1965), and the CDC 3300 (December 1965). The final machine in the series, the CDC 3500, was released in March 1967 and used integrated circuits instead of discrete components. The 3300 and 3500 had optional relocation capabilities, floating-point arithmetic, and BDP (Business + Data Processing) instructions. These machines were targeted towards business and commercial computing. The 3150 Control Data Corporation's CDC 3150 was described as a "batch computer," and it included a FORTRAN and a COBOL compiler. Its console looked like this. Instruction sets The instruction set of the upper 3000 series was composed mostly of 24-bit instructions (packed two per word), but also contained some 48-bit instructions. The lower 3000 was based on a 24-bit subset of those available on the upper 3000 systems. It was therefore possible to write programs which would run on all 3000 systems. And as these systems were based on the prior 1604