connected) and logically(what uses should the various memory locationns be put to)in addition mass storage the holding zone for programs and deta must also be decided upon. The first part of the physical memory question the hardware to use was easily sloved at the time pc was first designed
memory chips holding 16,384 bytes 16k were the most plentiful and cost affective,they were also the basis most competing computers.the least expensive and most popular of these stored their bytes in a one dimenstional array,giving 16,384 places to store a single memory bit,other chips might store four bits at a location,half a byte or a nibble at a time ,a minimum of eight chips of these one dimensional chips are required to hold a byte of iformation,because of their one dimensional architecture.
IBM added one more chip to the basic and minimal eight,in the mainframe business data integrity is extremely imporant so large computers use complex schemes for detecting and possibly correcting memory errors.IBM decided to include of form of memory quality in surance in the pc a system that would randomly detect if a memory bit should fail.The simplest possible detection scheme involves adding up all the bits in the byte then adding in a special parity bit to insure the total is always even,if one bit changes,the total comes out odd and an error must have occurred.The extra parity check bit requires one additional RAM chip consequently the PC was equipped with none memory chips.
With a bit of prescience (the knowledge that most programs wont run with so little memory as 16k IBM provided palces for adding more memory.A total of 27 empty sockets allowed you to plug up to 64 kilobytes of memory into the PC.with an eye to the future ,IBM even mad provisions for installing boards containing extra RAM,allowing the system to be expanded up to 512k at the time more than any program could possibly require.The IBM engineers reserved the other half of the addressing range of the 8088 for special purposes,some locations were used for videos memory others for the permanently recorded programs in ROM that are collectively called the basic input/output system,only a small fraction of this reserved memory area was actually put to use but IBM made sure it was there should it ever be needed,in fact only about 20k for the BIOS in mass storage IBM almost indiscriminately exploited the same options other personal computer makers had used,miniature (for the time)7 inch floppy disks were a natural both because of their use in other small computers and because of IBM's experience with their larger cousins 8 inch drives in other IBM products such as its display writer word processor.
again no one at the time foresaw a need for huge amounts of mass storage,so IBM elected to use only one side of the potentially two sided disks limiting capacity to 160 kilobytes .although puny by today's standards,that capacity was substantially greater than the 80 to 130 kilobytes used in other small computers at the time.IBM also hedged its mass storage bet by including a cassette port as part of the first pc instead of buying a 500$ floppy disk drive,you could use your tape recorder to remmember programs and data even exchange files with your friends cassette tape is of course slow and in convenient a particularly poor match for the pc,but should hobbyists actually be the major market for the some what undirected PC the cassette port would undoubtedly find users.
All computers need a programming language and IBM gave the PC basic the beginners all purpose symbolic instruction code weighting in favor of IBM's including basic its pc was the acceptance of the language in the small computer industry and among hobbyists the small size of the language that made it unable on machines with limited memory and IBM's own experience with basic in the 5100 .another programming language APL(short for a programming language) was also used on the 5100 and in many cases preferred by the users of the computer.how ever basic won out.much to the consternation of compatible makers ever
since IBM stuffed a rudimentary form the basic into the ROM chips(un changeable hardware) of the pc because mass storage was essentially optional in the first PC's the machines would have been little more than vegetables without an internal programming language basic was always there waiting for you even if you had no disk drive ready to save and load programs from cassette tape..
