instructions. A remarkable feature in the pre-microprogramming era was a "compatibility mode" switch that allowed it to run 1401 programs without change. 7010 was a faster and exactly compatible version of 1410. The IBM System/360 Model 30 could be ordered with a 1401 compatibility microprogram feature. Several 1400 series peripherals were adapted for use with System/360. Honeywell's Honeywell 200 provided approximate 1401 compatibility through a combination of architectural similarity and software support. Field and character coding With the 1400 series, the smallest addressable unit in core-storage is called a character. The 1400 stores alphameric characters internally in binary-coded decimal (BCD) form, spanning six bits called BA8421. When the character is an operation code or is the first character in a field, another bit, called the "word mark", is included. An odd parity bit, called "C", is also included. Arithmetic is 10-based with the one's position at the high- and the most-significant decimal digit at the low-address end of a multi-digit field, thus of ″big-endian″ style. This pertains for both, the (possibly indexed) address calculation for the access of operands and for the various operands of the arithmetic instructions. Whereas an address field in an instruction, designating an operand, is of fixed length (which depends on the size of the storage), the numeric operands of arithmetic instructions may be of arbitrary (positive) length. The word mark approach allows the 1410 to access a field (depending on the instruction to be performed) at either end, so that the most efficient access can be chosen. This way, the compiler of a higher-level programming language has to take care of the initial increment of the operand address (by operand length minus 1) for example, for add, subtract, or multiply instructions. Programming languages Programming languages for the 1400 series included Symbolic Programming System (SPS, an assembly language), Autocoder (a more fully featured assembly language), COBOL, FORTRAN, Report Program Generator (RPG), and FARGO. Retirement The 1400 series was replaced by System/360 and, later, by low-end machines like the IBM System/3, System/32, System/34, System/36, System/38, and AS/400. The 1400s were officially withdrawn in the early 1970s, however some 1400-series peripherals were still marketed with third-generation systems. Two 1401 computers have been restored to full operational status at the Computer History Museum. Notes References IBM Archives: Pre-360 IBM Mainframe Family tree & chronology. A source for 1401, 1460 components. A source for 1410/7010 components. External links Many IBM