OpenOffice.org is an office suite designed for word processing, spreadsheets, presentations, graphics and databases. It lets you create mathematical equations with a graphic user interface or by directly typing your formulas into the equation editor. You can also produce everything from simple diagrams to dynamic 3D illustrations... (
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The program works with the following extensions: 
oxt, 
sxm, 
pot, 
sxw, 
pps, 
vor, 
dot, 
sda, 
xlw, 
smf, 
sdc, 
odb, 
odf, 
sdd, 
pdt, 
odg, 
sds, 
psw, 
odm, 
sdw, 
pwd, 
odp, 
sgl, 
pwi, 
ods, 
stc, 
pwt, 
odt, 
std, 
xlt, 
otg, 
sti, 
sqf, 
oth, 
stw, 
smd, 
otp, 
sxc, 
sfs, 
ots, 
sxd, 
scc, 
ott, 
sxi and 
fods