Program logic and design chapter 7

Why are file sizes usually expressed in kilobytes

Because that byte is so small

Gigabytes

Billions of bytes

When discussing computer storage

Temporary permanent referred to volatility not length of time

Two broad categories of computer files

Text files, and binary files

What does .txt indicate

A plain text file

Kilobytes

Thousands of bytes

What is .jpg a file format for and what is its characteristics?

Used as an extension on image files in joint photographic experts group format.

delimiter

A character that separates data entries from one another.. comma, semicolon, or tab character.

An example of a filenames extension frequently designates the software that will be used to open a file

A file that uses the extension.docx Will usually be opened by Microsoft word by default

file name extension

A group of characters added to the end of a file name that describes the type of the file. For example the full name of the file might be JanuaryPayroll.txt in which the .txt is the file name extension.

Byte

A small unit of storage

filename

An identifying name given to a computer file that frequently describes the contents, for example JanuaryPayroll or previousMonthSales.

What is .dat extension

Common extension for data file

To use data files in your programs, you need to understand several file operations.

Declaring a file identifier, opening a file, reading from a file and processing the data, writing to a file, closing A file

Sorting in ascending order

Describes records sorted in order from lowest to highest values

Each file occupies space on a section of a storage device

Each file has a size. The sizes are measured in bytes.

Each file has specific times associated with it

Ex. It's creation time and the time it was last modified

What are some things Text files might include

Facts and figures used by business programs, such as payroll file that contains employee numbers, names, and salaries.

Although their contents vary, files have many common characteristics such as

Filename, and filename extension

records

Group of fields that go together for some logical reason. A random name, address, and salary aren't very useful but if they are your name, your address, and you're salary then that is your record.

Files

Groups of related records. The individual records of each student in your class might go together in a file card Students.DAT.

Database

Hold related file data in tables

An example of a byte

In a simple text file a byte holds only one character

Declaring a file identifier. Files are declared by giving each data type and identifier. examples

InputFile employeeData, OutputFile updatedData

characters

Letters, numbers, and special symbols, anything you can type from the keyboard even a space and tabs.

Megabytes

Millions of bytes

Directories and folders

Organization units on storage devices. Each can contain multiple files as well as additional directories

sequential file

Reads all the records in the file from beginning to end, processing them one at a time

Persistent Storage

Some programmers prefer this term instead of permanent storage. Because you can remove data from my files stored on a device such as a disc drive so it is technically not permanent. However the Daddo remains in the file even when the computer loses power so Unlike in RAM THE DATA PERSISTS

path

The combination of the disk drive plus the complete hierarchy of directories in which a file resides

Random Access Memory (RAM) or computer memory

Volatile, temporary storage that holds the program and data the CPU is presently processing. It is called temporary storage because its contents will be lost if electrical power to the computer is disrupted or the computer is turned off.

Close the file

When a program is finished using a file, it should do this. A close file is no longer available to your application

Data Hierarchy

When businesses store data items on computer systems, they are often stored in a framework called data hierarchy

Writing to the file

When you store data in a computer file on a persistent storage device

reading from a file

You never use the data values that are stored on a storage device directly. Instead you use a copy that is transferred into memory. When you copy data from a file on a storage device intoRAM you are "reading from a file"

computer file

a collection of data stored on a nonvolatile device in a computer system

Text files

contain data that can be read in a text editor because the data has been encoded using a scheme such as ASCII or Unicode

Binary files

contain data that has not been encoded as text. Examples include images and music.

permanent storage devices

hold nonvolatile data; examples include hard disks, DVDs, USB drives, and reels of magnetic tape

fields

lastName, middleInitial, streetAddress, or annualSalary

descending order

lists data in reverse alphabetical or sequential order. Highest to lowest values

Opening a file

locates the file on a storage device and associates a variable name within your program with the file