The Command Line, 1981
MS-DOS ran on nearly every PC for a decade, and it was learned one command at a time. This era gives you a simulated 386 with a working filesystem, so DIR, COPY, CHKDSK and batch files answer the way they did.
Classic shells track · 31 missions · boss mission, no written exam · free, no signup. Everything below runs in the browser terminal on the SERVBG home page.
What you will do
- list files and folders
DIRTim Paterson wrote DOS in 6 weeks, 1981. Microsoft paid $50,000 for it.
- show OS version
VERMS-DOS 6.22, 1994. Version numbers defined which software would run.
- list all commands
HELPThe entire OS fit on one 1.44MB floppy. Every byte was precious.
- clear the screen
CLSNo GUI, no mouse. CLS was your only refresh button.
- show or set the date
DATEEarly PCs had no real-time clock chip. You typed the date on every boot.
- show or set the time
TIMEBefore CMOS batteries, computers forgot everything when powered off.
- display a text file
TYPE README.TXTBefore .PDF, before .DOC — plain .TXT was the universal format.
- print text to screen
ECHO hello worldBatch files (.BAT) were millions of people's first taste of programming.
- show environment variables
SETAUTOEXEC.BAT ran on every boot. Tuning it was a rite of passage.
- show memory usage
MEMThe 640KB conventional memory limit shaped PC software for 15 years.
- check disk for errors
CHKDSKLost clusters, cross-linked files — FAT16 was fragile. CHKDSK ran at every crash.
- scan disk surface for bad sectors
SCANDISKSCANDISK replaced CHKDSK in DOS 6.2. Surface scan found physical bad sectors before data loss.
- defragment the hard drive
DEFRAGHDDs were fastest reading consecutive sectors. Fragmentation cut speed by 50% over months of use.
- copy files and subdirectories recursively
XCOPY /SXCOPY replaced COPY for tree copies. /S recurses dirs, /E includes empty dirs, /Y skips confirm.
- view or change file attributes
ATTRIBFour attributes: Read-only, Hidden, System, Archive. The basis of early file access control.
- enable command history and macros
DOSKEYBefore readline, there was DOSKEY. Macros like DOSKEY LL=DIR /W saved thousands of keystrokes.
- configure COM port or display
MODE COM1:9600,N,8,1Sound Blaster IRQ/DMA/I/O conflicts were a rite of passage. MODE and BLASTER= SET solved serial ports.
- open the DOS text editor
EDIT AUTOEXEC.BATAUTOEXEC.BAT ran every boot. One wrong line meant a non-booting PC — and a lesson never forgotten.
- inspect and patch executables
DEBUGDEBUG.EXE: hex editor, disassembler, raw memory writer. Every cracker in 1988 lived here.
- launch the QBasic IDE
QBASICQBASIC replaced GW-BASIC in 1991. Millions wrote their first structured program in it.
- create or delete disk partitions
FDISKFDISK /MBR could revive a virus-infected boot sector. One wrong move wiped everything. Respect it.
- run Interlnk server for direct PC transfer
INTERSVRInterlnk/Intersvr: file transfer over a null modem cable. Predated USB. A LAN for two laptops.
- redirect ECHO output into a new file instead of the screen
ECHO HELLO WORLD > GREETING.TXTThe > operator reached DOS 2.0 in 1983, borrowed from Unix. Output no longer had to go to a screen.
- append output to a file without erasing what is already there
ECHO SEE YOU LATER >> GREETING.TXTOne > too few and >> would silently wipe a file. A generation of BBS sysops learned this the hard way.
- pipe output through MORE.COM to page it one screen at a time
TYPE GREETING.TXT | MOREDOS piping was a trick: COMMAND.COM wrote the first program's output to a temp file, then fed it to the second. Unix pipes never touched disk.
- filter DIR output for matching lines with FIND
DIR | FIND "BAT"FIND.EXE was DOS's answer to grep — one literal string, no regex, and proud of it.
- create a file by typing it straight from the keyboard — no editor needed
COPY CON HELLO.BATCON was the console device. COPY CON FILENAME, then text, then F6/^Z — how millions wrote their first file before EDIT.COM existed.
- run the batch file you just created — watch it expand %NAME% and check IF EXIST live
HELLO.BATCOMMAND.COM searched the current directory then PATH for a matching .COM, .EXE, then .BAT — in that order.
- define an environment variable for the current session
SET NAME=SERVBGAUTOEXEC.BAT was mostly a wall of SET lines. Get one wrong and a program couldn't find its own data.
- branch batch logic on whether a file exists
IF EXIST HELLO.BAT ECHO FOUND ITIF EXIST / IF NOT EXIST / IF ERRORLEVEL were the entirety of DOS batch logic. No loops without GOTO.
- Boss missionenable disk cache
SMARTDRVSmartDrive cut boot times 40% by caching disk reads. Write-back mode was faster but risky on crash.
Certificate
This is one of the original eras, so it ends at the boss mission: there is no written exam and no certificate for it. Clearing the boss marks the era complete and banks the XP. The expansion tracks (networking, Cisco IOS, FortiOS, containers, Kubernetes, cloud, operations, defence, models and the nine graphics eras) are the ones that carry exams.