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40 Cards in this Set
- Front
- Back
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What is a user defined data type? |
Is a data type based on the existing data type or other data type that is defined by the programmer It can be divided into Non-composite and composite data types |
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What is a non composite data type? |
It is a data type that does not reference to other data type |
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What is an enumerated data type? |
Is a non composite data type that is defined by given a list of possible values that has an implied order
A list of prescribed values are created for this user-defined data type, which is defined by the user An object of that data type can then be declared and assigned one of those prescribed values Much in the same way an INTEGER data type must be a number from 0 to thelargest recognised by the language a STRING must be a character in the UNICODE acceptable list a USER-DEFINED data type be within the user-defined list of prescribed values Enumerated values are ORDINAL meaning they have a specific order Allows for comparison statement |
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What are the advantages of user defined data type? |
When there’s no suitable data type is provided by the language used theProgrammer needs specify a new data type that meets the requirement of theprogram Ability to self-document user data structures Let’s user to group data of different types in a single variable |
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What is the disadvantage of user defined data type? |
Only possible if a programming language offers support for the construct |
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What are the examples of uses of non composite data type? |
Ex: Integer, Real, String, Char, Pointer |
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What is the pointer data type? |
Non composite data type that uses the memory address of the data |
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What are composite data types? |
A data type that refers to any other data type in its type definitions |
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What is a set? |
A given list of unordered elements that can use theory operations |
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What is a class? |
The composite data type that includes variables of given data types and methods |
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What is serial file organization? |
A method of file organization in which the records of data are physically stored in a file from one after another in the order that they were added to the file New records will be recognized at the end of the file It uses temporary file soring transactions to be made to more permanaent files |
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What is sequential file organization |
A method of file organization in which records of data are physically stored in the file one after another in a given order The order is based on the key field or the records |
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What is the random file organization? |
A method of file organizations which records the data physically in any available position The location of file can be found by using hashing algorithm |
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What is file access? |
The methods used to physically find a record in the file |
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What is sequential access? |
A method of file access that uses to physically find the record in the file one after another from the start of the file until the file is found |
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What are the types of sequential access? |
SERIAL FILE -> Any new records are recognized at the end of the file SEQUENTIAL FILE -> If a particular record needs to be searched for it checks the records until it is found or the key field that is being checked is greater than the key field that is being searched -> Any new records to be stored are inserted in the correct place in the file -> It is efficient when every record in the file needs to be processed |
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What is direct access? |
To physically find a record in a file without other records being physically read It allows specific records to be found more quickly than sequential access It is required when an individual record from a file needs to be processed |
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How direct access works for a sequential file? |
An index of all key fields is kept and used to look up the address of the file location where a given record is stored |
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How direct access works for a random access file? |
A hashing algorithm is used on the key field to calculate the address of the file location where a given record is stored |
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What are hashing algorithms |
A mathematical formula used to perform a calculation on the key field of the record The result of the calculation gives the address where the record should be found |
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How to write records |
1) Choose a suitable number and divides this number by the value in the key field 2) Remainder form the division identifies the address in the file for storage of the record |
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How does collision occur? |
It occurs when there is same remainder and same address in both files when they use the same file location |
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How to read a record from a file using direct access? |
The address of the location to read from is calculated using the hashing algorithm and the key field of the record stored there is read But before using that record, the key field must be checked against the original key field to ensure they match If the key fields don't match then the following records need to be read until a match(open hash) is found or the overflow area needs to be searched for a match(close hash) |
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What is normalisation? |
It ensures more bits are assigned to the mantissa so accuracy is ensured |
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What happens when more bits are allocated for the exponent? |
The range of numbers increases and the accuracy will decrease |
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What happens when more bits are allocated for the mantissa ? |
The accuracy will increase but the range will decrease |
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What is the largest positive number |
0 111 111 111 11 | 0111 |
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What is the smallest positive number |
01000 000 | 1000 |
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What is the largest magnitude negative number |
1 000 000 000 00 |0111 |
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What is the smallest magnitude negative number |
1 0 111 111|1000 |
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What are the problems of floating point numbers? |
Overflow -> If the result produces a number that exceeds the maximum possible value that can be stored in the mantissa and exponent Underflow -> If the result produces a number less than the smallest number that can be stored Unable to store 0 -> Mantissa must be 0.1 or 1.0 which don't allow for a 0 value |
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What are the advantages of using serial file organization? |
No need to re-sort data every time there is new data added Only a small file so searching will require little processing New records can be easily apprenhended |
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How to add a record added to the random file? |
The record is hashed to produce the home location of the file If the location is free then insert the data else use the overflow method to find the free location |
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What is the purpose of user-defined data type? |
To create a new data type from existing data types • To allow data types not available in a programming language to beconstructed To extend the flexibility of the programming language |
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What is the consequence and justification of storing the binary number in a normalized floating point representation as a floating point number in this system? |
Consequence • The accuracy of the number would be reduced Justification because the least significant bits of the original number have been lost |
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Compare sequential and serial methods of file organization. |
Serial files are stored in chronological order Sequential files are stored with ordered records which are stored in the order of the key field In serial files, new records are added in the next available space In sequential files, new records are inserted in the correct position. |
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State the most suitable method of file access when a record is referenced by a unique address on a disk-type storage medium. |
Direct |
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State the most suitable method of file access when a bank stores its data records in ascending order of account number. |
Sequential |
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State when underflow occurs in a binary floating-point system. |
Following an arithmetic operation when the result is too small to be precisely represented in the available system |
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Why some binary representations can lead to rounding errors? |
There is no exact binary conversion for some numbers. More bits are needed to store the number than are available |
