The IBM Automatic Sequence Controlled Calculator (ASCC), called the Mark I by Harvard University, was the first large-scale automatic digital computer in the USA. International Business Machines Corporation abbreviated IBM and nicknamed "Big Blue", is a multinational Computer Technology A computer is a Machine that manipulates data according to a list of instructions. The United States of America —commonly referred to as the It is considered by some to be the first universal calculator. The claim to be the first programmable electronic computer is that of the Colossus computer. The Colossus machines were electronic Computing devices used by British codebreakers to read Encrypted German messages during
The electromechanical ASCC was devised by Howard H. Aiken created at IBM, shipped to Harvard in February 1944, and formally delivered there on August 7, 1944. Howard Hathaway Aiken ( March 8, 1900 – March 14 1973) was a pioneer in Computing, being the primary engineer behind IBM Year 1944 ( MCMXLIV) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. Events 322 BC - Battle of Crannon between Athens and Macedon following the death of Alexander the Great. Year 1944 ( MCMXLIV) was a Leap year starting on Saturday (link will display full calendar of the Gregorian calendar. The main advantage of the Mark I was that it was fully automatic—it didn't need any human intervention once it started. It was the first fully automatic computer to be completed. It was also very reliable, much more so than early electronic computers. It is considered to be "the beginning of the era of the modern computer" and "the real dawn of the computer age". 
The building elements of the ASCC were switches, relays, rotating shafts, and clutches. A switch is a mechanical device used to connect and disconnect an electric Circuit at will A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. A clutch is a mechanism for transmitting rotation which can be engaged and disengaged It was built using 765,000 components and hundreds of miles of wire, amounting to a size of 51 feet (16 m) in length, eight feet (2. An electronic component is a basic electronic element usually packaged in a discrete form with two or more connecting leads or metallic pads 4 m) in height, and two feet (~61 cm) deep. It had a weight of about 10,000 pounds (4500 kg). The basic calculating units had to be synchronized mechanically, so they were run by a 50-foot (~15. 5 m) shaft driven by a five-horsepower (4 kW) electric motor. From the IBM Archives:
The Automatic Sequence Controlled Calculator (Harvard Mark I) was the first operating machine that could execute long computations automatically. A project conceived by Harvard University's Dr. Howard Aiken, the Mark I was built by IBM engineers in Endicott, N. Y. A steel frame 51 feet long and eight feet high held the calculator, which consisted of an interlocking panel of small gears, counters, switches and control circuits, all only a few inches in depth. The ASCC used 500 miles of wire with three million connections, 3,500 multipole relays with 35,000 contacts, 2,225 counters, 1,464 tenpole switches and tiers of 72 adding machines, each with 23 significant numbers. It was the industry's largest electromechanical calculator. 
The Mark I had 60 sets of 24 switches for manual data entry and could store 72 numbers, each 23 decimal digits long.  It could do three additions or subtractions in a second. A multiplication took six seconds, a division took 15. 3 seconds, and a logarithm or a trigonometric function took over one minute.
The Mark I read its instructions from a 24 channel punched paper tape and executed the current instruction and then read in the next one. An instruction set is a list of all the instructions and all their variations that a processor can execute Punched tape or paper tape is a largely obsolete form of Data storage, consisting of a long strip of paper in which holes are punched to store data It had no conditional branch instruction. A branch (or jump on some Computer architectures, such as the PDP-8 and Intel x86) is a point in a Computer program where the This meant that complex programs had to be physically long. A loop was accomplished by joining the end of the paper tape containing the program back to the beginning of the tape (literally creating a loop). This separation of data and instructions is known as the Harvard architecture (although the exact nature of this separation that makes a machine Harvard, rather than Von Neumann, has been obscured with the passage of time, see Modified Harvard architecture). The Harvard architecture is a Computer architecture with physically separate storage and signal pathways for instructions and data The Modified Harvard Architecture is a variation of the Harvard computer architecture that allows the contents of the instruction memory to be accessed as if it were data The first programmers of the Mark I were Richard Milton Block, Robert Campbell, and computing pioneer Grace Hopper. Rear Admiral Grace Murray Hopper ( December 9 1906 – January 1 1992) was an American Computer scientist and United 
The 24 channels of the input tape were divided into 3 fields of 8 channels. Each accumulator, each set of switches, and the registers associated with the input, output, and arithmetic units were assigned a unique identifying index number. In a Computer 's central processing unit ( CPU) an accumulator is a register in which intermediate arithmetic and logic results are stored In Digital electronics, especially Computing, a hardware register stores bits of information in a way that all the bits can be written to or read out simultaneously In Computing, input/output, or I/O, refers to the communication between an Information processing system (such as a Computer) and the outside In Computing, an arithmetic logic unit ( ALU) is a Digital circuit that performs Arithmetic and Logical operations These numbers were represented in binary on the control tape. The binary numeral system, or base-2 number system, is a Numeral system that represents numeric values using two symbols usually 0 and 1. The first field was the binary index of the result of the operation and the second, the source datum for the operation. The third field was a code for the operation to be performed. In computer technology an opcode ( op eration code) is the portion of a Machine language instruction that specifies the operation to be performed In Computer science, an instruction is a single operation of a processor defined by an Instruction set architecture. 
At the dedication ceremony, Aiken failed to mention the involvement of IBM in designing and building the computer. IBM was not pleased with this, and parted ways with Aiken.  IBM named the computer the ASCC but Harvard and Aiken renamed it the Mark I. IBM went on to build the SSEC. The IBM Selective Sequence Electronic Calculator ( SSEC) also called Poppa, was an electromechanical Computer built by IBM, finished in January
The Mark I was followed by the Harvard Mark II (1947 or 1948), Mark III/ADEC (September 1949), and Harvard Mark IV (1952) – all the work of Aiken. The Harvard Mark II was an electromechanical computer built at Harvard University under the direction of Howard Aiken and was finished in 1947 The Harvard Mark III, also known as ADEC (for A iken D ahlgren E lectronic C alculator was an early computer that was partially electronic The Harvard Mark IV was an electronic stored-program Computer built by Harvard University under the supervision of Howard Aiken for the United States The Mark II was an improvement over the Mark I, but it also used electromechanical relays. The Mark III used some electronic components and the Mark IV was all-electronic, using solid state components. Solid-state Electronic components devices and systems are based entirely on the Semiconductor, such as Transistors Microprocessor chips and The Mark III and Mark IV used magnetic drum memory and the Mark IV also had magnetic core memory. Drum memory is a magnetic Data storage device and was an early form of Computer memory widely used in the 1950s and into the 1960s invented by Gustav Tauschek Magnetic core memory, or ferrite-core memory, is an early form of Random access Computer memory. The Mark II and Mark III went to the US Navy base at Dahlgren, Virginia. Dahlgren is a Census-designated place (CDP in King George County, Virginia, United States. The Mark IV was built for the US Air Force, but it stayed at Harvard.
The Mark I was eventually disassembled, although portions of it remain at Harvard in the Science Center.
A story told by Grace Hopper about staff finding the first computer bug, a moth crushed in a relay of the Mark I, was widely misinterpreted as the origin of the term bug in the sense of a technical problem. Rear Admiral Grace Murray Hopper ( December 9 1906 – January 1 1992) was an American Computer scientist and United See Computer bug - Etymology. A software bug (or just “bug” is an error flaw mistake Failure, fault or “undocumented feature” in a Computer program that prevents it
|Name||First operational||Numeral system||Computing mechanism||Programming||Turing complete|
|Zuse Z3 (Germany)||May 1941||Binary||Electro-mechanical||Program-controlled by punched film stock||Yes (1998)|
|Atanasoff–Berry Computer (USA)||Summer 1941||Binary||Electronic||Not programmable—single purpose||No|
|Colossus (UK)||December 1943||Binary||Electronic||Program-controlled by patch cables and switches||No|
|Harvard Mark I – IBM ASCC (USA)||1944||Decimal||Electro-mechanical||Program-controlled by 24-channel punched paper tape (but no conditional branch)||Yes (1998)|
|ENIAC (USA)||November 1945||Decimal||Electronic||Program-controlled by patch cables and switches||Yes|
|Manchester Small-Scale Experimental Machine (UK)||June 1948||Binary||Electronic||Stored-program in Williams cathode ray tube memory||Yes|
|Modified ENIAC (USA)||September 1948||Decimal||Electronic||Program-controlled by patch cables and switches plus a primitive read-only stored programming mechanism using the Function Tables as program ROM||Yes|
|EDSAC (UK)||May 1949||Binary||Electronic||Stored-program in mercury delay line memory||Yes|
|Manchester Mark I (UK)||October 1949||Binary||Electronic||Williams cathode ray tube memory and magnetic drum memory||Yes|
|CSIRAC (Australia)||November 1949||Binary||Electronic||Stored-program in mercury delay line memory||Yes|