array; 20,000-and-above on a 20K core array. On a 10K core array, invalid addresses are detected by the address-bus validity check." 1962 A reference to a "4k IBM 1401" meant 4,000 characters of storage (memory). 1963 Ludwig uses kilobit in the decimal sense DEC Serial Drum Type 24 "Drums are equipped to store either 64, 128, or 256 data blocks, providing a memory capability of 16384, 32768, or 65536 computer words" (no abbreviations) Honeywell 200 Summary Description "The main memory is a magnetic core ... The memory unit supplied as part of the basic central processor has a capacity of 2,048 characters, each of which is stored in a separate, addressable, memory location. This capacity may be expanded in modular increments by adding one 2,048-character module and additional 4,096-character modules." "Random access disc file and control (disc capacities of up to 100 million characters are available.)" "Up to eight drum storage units can be connected to the Model 270 Random Access Drum Control. Each drum provides storage for 2,621,441 characters, allowing a total capacity of approximately 21 million characters." 1964 Gene Amdahl's seminal April 1964 article on IBM System/360 used 1K to mean 1024. Leng, Gordon Bell, et al., use K in the binary sense: "The computer has two blocks of 4K, 18-bit words of memory, (1K=1024 words), attached to its central processor" Data Processing Division press release distributed on April 7, 1964. "System/360 core storage memory capacity ranges from 8,000 characters of information to more than 8,000,000." IBM 7090/7094 Support Package for IBM System/360 – November "An IBM 1401 Data Processing System with the following minimum configuration is also required: 1. 4K positions of core storage" – ADDRESS SELECTION CONTROL APPARATUS – Filed April 6, 1964 "To facilitate understanding of the invention, the main storage area has been illustrated as being of 8K capacity; however, it is to be understood that the main storage area may be of larger capacity (e.g., 16K, 32K or 64K) by storing address selection control data in bit positions '2', '1' and '0' of M register 197, respectively." 1965 "Each IBM 2315 disk cartridge can hold the equivalent of more than one million characters of information. "One method of designing a slave memory for instructions is as follows. Suppose that the main memory has 64K words (where K=1024) and, therefore, 16 address bits, and that the slave memory has 32 words and, therefore, 5