There appeared non-numeric, symbolic data stored together with numeric data in the form of the record structure; Input data are stored in the form of files independently of the processing program; the program holds the file record description; Processing time is less than the data input/output time (Tproc.<Texchng ) Files are reusable; The output result is formed as a document easily available for user analysis The typical information tasks are ones in the field of organization management. For example, the competition percentage calculation (the number of applications for one vacancy) in processing applications from the applicants for higher education. Two files F1 – PLAN and F2 – APPLICATION with the structure shown in Fig. 1 are enough for solving this task. The necessity for independent data storing (for example, file F2) is due not only to the considerable volume, but also the necessity of its independent update as new applications come or the data are changed (for example, the faculty applied to). For the purpose of such updating, a special program was commonly used, inputting data from punched cards and punched tapes (Fig. 1.1.2). Evidently, it is necessary to reuse the data since it is important for the administration to know the competition percentage is not less than once a day. In this case the program runs even if there was not a single application handed for the previous day. The second computer generation is characterized by the following features essentially affecting the information task characteristics: Basic elements are semi-conductor instruments; Performance is hundreds of thousand operations per second; The required space and the weight are a few times less than before; The RAM size is about 250 Kb; The external (peripheral) storage devices are magnetic tapes, drums and others, for example, the alphabetic-numeric printing devices, devices for transmitting information via communication channels. It should be that at the beginning of 60s there prevailed the task-specific approach in using the input data, its characteristics being that for each program its <own> data files were used. Therefore, in order to get a report concerning applicant distribution by regions, from where and with what kinds of secondary qualification they apply, there are two tasks and their corresponding programs, each with its own file as shown in Fig. 1.1.3. If these programs were developed at the same time and by the same
study R6 Specialty Specialty chair Study beginning year Current year admission plan Specialty preparation information R7 Specialty year Subject Total hours Classroom hour Lab hour Practical hour plan section (left part) R8 Specialty Entry year Subject Semester Weeks in semester Classroom lessons type Study plan section (right part) R9 Semester Subject Group Lesson type Hour Quantity Lecturer # Chair Chair Study warranty R10 Subject Subject abbreviation State program standard Fig. 2.5.1 2.5.2. Data fragment, representing the study process organization in a higher education institution (constructed on a set of relations shown in point 2.5.1)
. . . R07109 Ivanov I.I. 01.01.78 М R07109 Math. Analysis 5 950 R07110 P.P. 23.02.78 М R07110 Math. Analysis 4 900 R07112 Sidorova Е.I. 8.03.79 F R07112 Math. Analysis 5 1000 . . . R07109 Ivanov I.I. 01.01.78 М R07109 Programming 5 980 R07110 Peter P.P. 23.02.78 М R07110 Programming 5 950 R07112 Sidorova Е.I. 8.03.79 F R07112 Programming 4 850 . . . R07109 Ivanov I.I. 01.01.78 М R07109 DB and KB 4 850 R07110 Peter P.P. 23.02.78 М R07110 DB and KB 5 980 R07112 Sidorova Е.I. 8.03.79 F R07112 DB and KB 4 800 Fig. 3.2.1.7 Physically this file does not exist, but for the program processing all the operations may be performed as if it were a real file. As the relational fields several fields may be used. So the second file may be related with the following ones (Fig. 3.2.1.8) by the fields: student number and subject. Student # Subject Month Absence Quantity Attestation score . . . R07109 Math. Analysis September 10 5 R07110 Math. Analysis September 0 5 R07112 Math. Analysis September 40 3 . . . R07109 Math. Analysis October 6 4 Р07110 Math. Analysis October 16 4 R07112 Math. Analysis October 0 5 . . . R07109 Programming December 0 5 R07110 Programming December 20 3 R07112 Programming December 10 5 . . . R07109 DB and KB February 0 5 R07110 DB and KB February 6 4 Р07112 DB and KB February 8 5 . . . Р07109 DB and KB May 6 5