Answer by taking a quote from the following article:

Mohammed Hussein redirects here; for the Muslim cleric, see Muhammad Ahmad Hussein. Babrak Karmal (Dari/Pashto: bbrkh khrml, born Sultan Hussein; 6 January 1929 - 1 or 3 December 1996) was an Afghan politician who was installed as president of Afghanistan by the Soviet Union when they invaded in 1979. Karmal was born in Kamari and educated at Kabul University.

When he came to power, Karmal promised an end to executions, the establishment of democratic institutions and free elections, the creation of a constitution, and legalization of alternative political parties. Prisoners incarcerated under the two previous governments would be freed in a general amnesty. He promised the creation of a coalition government which would not espouse socialism. At the same time, he told the Afghan people that he had negotiated with the Soviet Union to give economic, military and political assistance. The mistrust most Afghans felt towards the government was a problem for Karmal. Many still remembered he had said he would protect private capital in 1978--a promise later proven to be a lie.  Karmal's three most important promises were the general amnesty of prisoners, the promulgation of the Fundamental Principles of the Democratic Republic of Afghanistan and the adoption of a new flag containing the traditional black, red and green (the flag of Taraki and Amin was red). His government granted concessions to religious leaders and the restoration of confiscated property. Some property, which was confiscated during earlier land reforms, was also partially restored. All these measures, with the exception of the general amnesty of prisoners, were introduced gradually. Of 2,700 prisoners, 2,600 were released from prison; 600 of these were Parchamites. The general amnesty was greatly publicized by the government. While the event was hailed with enthusiasm by some, many others greeted the event with disdain, since their loved ones or associates had died during earlier purges. Amin had planned to introduce a general amnesty on 1 January 1980, to coincide with the PDPA's sixteenth anniversary.  Work on the Fundamental Principles had started under Amin: it guaranteed democratic rights such as freedom of speech, the right to security and life, the right to peaceful association, the right to demonstrate and the right that "no one would be accused of crime but in accord with the provisions of law" and that the accused had the right to a fair trial. The Fundamental Principles envisaged a democratic state led by the PDPA, the only party then permitted by law. The Revolutionary Council, the organ of supreme power, would convene twice every year. The Revolutionary Council in turn elected a Presidium which would take decisions on behalf of the Revolutionary Council when it was not in session. The Presidium consisted mostly of PDPA Politburo members. The state would safeguard three kinds of property: state, cooperative and private property. The Fundamental Principles said that the state had the right to change the Afghan economy from an economy where man was exploited to an economy were man was free. Another clause stated that the state had the right to take "families, both parents and children, under its supervision." While it looked democratic at the outset, the Fundamental Principles was based on contradictions.  The Fundamental Principles led to the establishment of two important state organs: the Special Revolutionary Court, a specialized court for crimes against national security and territorial integrity, and the Institute for Legal and Scientific Research and Legislative Affairs, the supreme legislative organ of state, This body could amend and draft laws, and introduce regulations and decrees on behalf of the government. The introduction of more Soviet-style institutions led the Afghan people to distrust the communist government even more.

what was the fundamental principles?
Karmal's three most important promises were the general amnesty of prisoners, the promulgation of the Fundamental Principles of the Democratic Republic of Afghanistan and the adoption of a new flag