Updating help needed

I have a desktop mac and a mac notebook. They are both outdated I guess. They still work of course, but crash a lot, slow, and sometimes a sign comes up telling me this is outdated.

I restored several times over the years by CD's I had, not really knowing what I was doing I know, not smart.....

So, they both are described the same:

Laptop and desktop

Mac OS X
Version 10.5.8
Processor 2 GHz Intel Core 2 Duo
Memory 1 GB 667 MHz DDR2 SDRAM

I would like to bring them up to date and I feel they are worth saving as I am not a heavy computer user. Maybe an hour a day at the most and I don't do much except forums, a couple chats, research and youtube, etc.

I don't think I used the notebook more than 50 times since I bought it.

Would someone please give me instructions how to update?
Do I just buy a CD called snow tiger or something like that and install it?
Can I just jump to the most recent that is out. I think it is called Yosemite?
Or do I have to buy each disc to bring me up to date? Or do I need to send these to the junk yard and buy a new mac?

Your help will be appreciated as I really do need it explained to me so I can understand. I am not completely stupid, but I am not computer savvy either.

 

ok Bruno, one moment and I will get it........

PS:

I don't have any files to move anywhere. I don't need anything saved, etc.

I just use these computers for surfing around a bit.

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Is this the info Bruno?


Hardware Overview:

Model Name: iMac
Model Identifier: iMac7,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 1 GB
Bus Speed: 800 MHz
Boot ROM Version: IM71.007A.B03
SMC Version (system): 1.20f4
Serial Number (system): W8739MW8X85
Hardware UUID: 00000000-0000-1000-8000-001B63A702B8

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This is what the notebook says:

Hardware Overview:

Model name: MacBook
Model Identifier: MacBook3,1
Processor Name: Intel Core 2 Duo
Processor Speed 2 GHz
Number of Processors: 1
Total Number of cores: 2
L2 Cache: 4MB
Memory 1GB
Bus Speed: 800 MHz
Boot Rom Version MB31.008D.800
SMC Version *system) 1.24f3
Serial number W8746E53Z62
Hardwar UUID: A25B6BAF-EAF4-5B70-BDEC-FB61CEB34908
Sudden Motion Sensor:
State Enabled

 

Wow, that was fast help Bruno. Thanks

Couple questions....

Can I use the same Snow Leopard on BOTH the laptop and desk model. Can I order it on line at the mac shop?

Also, if I want to to this again when it tells me I am outdated again, how to I add RAM? Is that a disc also?

 

ok Bruno, thanks so much. I will get the snow leopard for now and install on both. Then worry about the ram when I start running into more problems, maybe by then I will just get a new computer or take these in to a professional to get the ram put in....

Great help Bruno....