disk drive business), stated in a Wall Street Journal interview that the RAMAC unit weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes. According to Munce, the storage capacity of the drive could have been increased beyond five megabytes, but IBM's marketing department at that time was against a larger capacity drive, because they did not know how to sell a product with more storage. Programming the 305 involved not only writing machine language instructions to be stored on the drum memory, but also almost every unit in the system (including the computer itself) could be programmed by inserting wire jumpers into a plugboard control panel. Architecture System architecture was documented in the 305 RAMAC Manual of Operation. The 305 was a character-oriented variable "word" length decimal (BCD) computer with a drum memory rotating at 6000 RPM that held 3200 alphanumeric characters. A core memory buffer of 100 characters was used for temporary storage during data transfers. Each character was six bits plus one odd parity bit ("R") composed of two zone bits ("X" and "O") and remaining four binary bits for the value of the digit in the following format: X O 8 4 2 1 R Instructions could only be stored on 20 tracks of the drum memory and were fixed length (10 characters), in the following format: T1 A1 B1 T2 A2 B2 M N P Q Fixed-point data "words" could be any size from one decimal digit up to 100 decimal digits, with the X bit of the least significant digit storing the sign (signed magnitude). Data records could be any size from one character up to 100 characters. Drum memory The drum memory was organized into 32 tracks of 100 characters each. The color code of this table is: Yellow – Storage Blue – Arithmetic Green – Input/output Red – Special function L and M select the same track, containing ten 10-character "Accumulators". As a destination L specifies addition, M specifies subtraction. (Numbers in these accumulators were stored in ten's complement form, with the X bit of the most significant digit storing the sign. The sign of each accumulator was also held in a relay. However the 305 automatically converted between its standard signed magnitude format and this format without the need for special programming.) J, R, and - do not select tracks on the drum,