This is a rather difficult and strange task to do without any utilities or cloud. You can check your phone's contacts app if it has some option to export contacts into some external file. Otherwise you will have to use some app from playstore like Super Backup which can save contacts in your sdcard.
By full backup, if you mean apps and data and contacts, sms etc, then Titanium Backup (pro recommended) is your one great chance.
Otherwise if you are rooted, you can use custom recovery to backup whole android including system and data (nandroid backup). But other then these, there's practically no way to backup without using 3rd party program (referring to ADB (which would need root, but can create an ultimate all in one backup of *everything you will ever need) and vendor softwares like Samsung Kies).
Otherwise if you are referring to without using any apps on phone, pc or cloud, thats basically impossible. Because:
1) App data-> There are lot other things. You can get APKs, and you can even try copying data from app data
/sdcard/Android/obb (for games) for which you will need root to get into /data directory (since we arent using any other app or program). But thats not it and you will probably end up in a corruption and ultimately reinstall app if you try manually copying/pasting the data, hence ultimately loosing that data. plus there's cache too which is a totally separate partition, so lets not take that into account either.
2) Contacts-> There isn't a simple txt where contacts are stored. You can though manually try extracting contacts as they are inside
/data/data/*.providers.contacts/databases/*.db (location varies phone to phone and vendor to vendor), but it would again need third party app such as some sort of SQL Editor to open it since they are in database format.
So it is practically impossible to do these tasks without using any external app or program.