Operating Systems and Office Software

Operating system

An operating system (OS) is system software that manages hardware and provides the platform on which application software runs. Examples: Windows, Linux, UNIX, macOS, Android.

Main functions

• Process management (scheduling programs on the CPU)
• Memory management
• File management
• Device management through drivers
• Security and user accounts
• Providing a user interface: GUI (icons, windows) or CLI (typed commands)

Types

Starting a computer is called booting: a cold boot starts from power-off, a warm boot is a restart.

Files and folders

A file is a named collection of data; a folder (directory) holds files and other folders in a tree structure. The extension shows the file type: .docx (document), .xlsx (workbook), .pptx (presentation), .pdf, .txt, .jpg.

Useful Windows keys: Win+E File Explorer, Win+L lock the PC, Alt+Tab switch apps, Alt+F4 close the active window, F2 rename, Shift+Delete delete permanently without the Recycle Bin, Ctrl+Shift+Esc Task Manager.

Word processor

Other examined features: mail merge (a main document combined with a data source of names and addresses), header and footer, page orientation (portrait or landscape), and tables.

Spreadsheet

A workbook contains worksheets; a cell is the intersection of a column (letter) and a row (number), for example B4. Every formula begins with =.

Common functions: SUM, AVERAGE, MAX, MIN, COUNT (counts cells holding numbers), COUNTA (counts non-empty cells), IF (tests a condition), COUNTIF and SUMIF (count or add cells meeting one condition), VLOOKUP (searches the first column of a table and returns a value from the same row).

Cell references

• Relative (A1): changes when the formula is copied.
• Absolute ($A$1): never changes.
• Mixed ($A1 or A$1): the part after the $ sign stays fixed.
• F4 cycles through the reference types while editing a formula.

Worked example: the formula =$A1+B$1 typed in C1 and copied to D2 moves one column right and one row down. $A1 becomes $A2 (column locked), B$1 becomes C$1 (row locked), so the result is =$A2+C$1.

Shortcuts: F2 edit the cell, Alt+= AutoSum, Ctrl+; current date, Alt+Enter new line inside a cell, Ctrl+1 Format Cells, F11 chart on a new chart sheet.

Charts: column or bar charts compare items, line charts show a trend over time, pie charts show each part as a share of a whole.

Presentation software

• F5 starts the show from the first slide; Shift+F5 from the current slide; Esc ends it.
• During a show, B blanks the screen to black and W to white.
• Ctrl+M inserts a new slide.
• Transition is the effect between slides; animation is the effect on an object within a slide.
• The Slide Master controls the layout and fonts of all slides; Slide Sorter view shows thumbnails for rearranging.

Exam pointers

• A real-time OS is defined by a guaranteed response time, not by speed alone.
• COUNT ignores text and blanks; COUNTA ignores only blanks.
• The $ sign locks whatever follows it: column, row or both.
• Ctrl+Enter is a page break in a word processor; Alt+Enter is a line break inside a spreadsheet cell.
• F5 starts a slide show; F7 checks spelling; F12 opens Save As; F2 edits a cell or renames a file.
• Pie for share of a whole, line for trend, column or bar for comparison.