First printing techniques
Printing is a process for reproducing text and images, typically with ink on paper using a printing press. It is often carried out as a large-scale industrial process, and is an essential part of publishing and transaction printing.
The earliest form of printing was woodblock printing, with existing examples from China dating to before 220 A.D. and Egypt to the fourth century. Later developments in printing include the movable type, first developed by Bi Sheng in China, and the printing press, a more efficient printing process for western languages with their more limited alphabets, developed by Johannes Gutenberg in the fifteenth century.
Movable type printing
Movable type is the system of printing and typography using movable pieces of metal type, made by casting from matrices struck by letterpunches. Movable type allowed for much more flexible processes than hand copying or block printing.
Copper movable type printing originated in China at the beginning of twelfth century. It was used in large-scale printing of paper money issued by the Northern Song dynasty.
Around 1040, the first known movable type system was created in China by Bi Sheng out of porcelain. Sheng used clay type, which broke easily, but Wang Zhen later carved a more durable type from wood by 1298 C.E., and developed a complex system of revolving tables and number-association with written Chinese characters that made typesetting and printing more efficient. Still, the main method in use there remained woodblock printing (xylography), which “proved to be cheaper and more efficient for printing Chinese, with its thousands of characters”.
Data that the human eye can’t see
Digital data, in information theory and information systems, are discrete, discontinuous representations of information or works, as contrasted with continuous, or analog signals which behave in a continuous manner, or represent information using a continuous function.
Although digital representations are discrete, the information represented can be either discrete, such as numbers and letters or continuous, such as sounds, images, and other measurements.
Symbol to digital conversion
Since symbols (for example, alphanumeric characters) are not continuous, representing symbols digitally is rather simpler than conversion of continuous or analog information to digital. Instead of sampling and quantization as in analog-to-digital conversion, such techniques as polling and encoding are used.
A symbol input device usually consists of a group of switches that are polled at regular intervals to see which switches are switched. Data will be lost if, within a single polling interval, two switches are pressed, or a switch is pressed, released, and pressed again. This polling can be done by a specialized processor in the device to prevent burdening the main CPU. When a new symbol has been entered, the device typically sends an interrupt to alert in a specialized format so that the CPU to read it.
Exploration of computer history
A computer is a general purpose device that can be programmed to carry out a set of arithmetic or logical operations. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem.
Conventionally, a computer consists of at least one processing element, typically a central processing unit (CPU) and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change the order of operations based on stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved and retrieved.
First general purpose computers
During the first half of the 20th century, many scientific computing needs were met by increasingly sophisticated analog computers, which used a direct mechanical or electrical model of the problem as a basis for computation. However, these were not programmable and generally lacked the versatility and accuracy of modern digital computers.
Alan Turing is widely regarded as the father of modern computer science.
Alan Turing is widely regarded as the father of modern computer science. In 1936, Turing provided an influential formalization of the concept of the algorithm and computation with the Turing machine, providing a blueprint for the electronic digital computer. Of his role in the creation of the modern computer, Time magazine in naming Turing one of the 100 most influential people of the 20th century, states: “The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine.”
